Image copyrightREUTERS

Image captionThe scandal is centred on the close relationship between Ms Park and Ms Choi

South Korea's President Park Geun-hye has become the country's first democratically elected leader to be forced from office.

That dubious honour was imposed on her when, on 10 March, judges unanimously upheld parliament's decision in December to impeach her over a corruption scandal.

That scandal, which has generated huge protests, centres on her relationship with an old friend, and has brought allegations of cult activities, influence-peddling and leaks of classified information.

What is the relationship at the heart of the scandal?

In 1974, Park Geun-hye's mother was killed by a North Korean spy who had intended to kill Ms Park's father, then-military leader Park Chung-hee. Ms Park, then aged 22, became a stand-in first lady for her widowed father.

Image copyrightAFP/GETTY

Image captionMs Choi has returned from abroad to face questioning

It was then she got to know Choi Tae-min, a pseudo-Christian leader who set up a cult called The Church of Eternal Life. He said he had been visited by the soul of Ms Park's late mother who asked him to guide her.

He became Ms Park's mentor, while also amassing considerable wealth and power.

When President Park senior was assassinated by his head of intelligence in 1979, there was speculation it was because the spy chief was worried the president was being manipulated by the man dubbed "the Korean Rasputin".

By this point Ms Park was firm friends with Mr Choi's daughter, Choi Soon-sil. Their critics believe Ms Choi perpetuated her father's habits.

Why has the friendship become problematic?

On 20 November, Ms Choi was charged with various offences, including abuse of authority, coercion, attempted coercion and attempted fraud. She is now on trial.

Few claims have been off-limits in the media coverage, with some reports going as far as suggesting the president is a puppet who hosted shamanist rituals at the presidential compound. But many of the lurid claims are unsubstantiated.

Image copyrightREUTERS

Image captionWith no immediate family, President Park came to rely too much on her friend, critics claim

Ms Choi is accused of using her presidential connections to pressure companies for millions of dollars in donations to two non-profit foundations she controlled.

The claims have even swept up Samsung in the investigation - the firm is one of eight that has admitted making payments to the foundation, but denies it did so in return for any favours.

President Park is alleged to have been personally involved, instructing Ms Choi and two presidential aides to collect money for the launch of Ms Choi's foundations, according to prosecution documents submitted to the court.

Image copyrightAFP

Image captionProtesters have marched in vast numbers to demand Ms Park stands down

Ms Choi is also accused of having received large numbers of confidential government documents from Ms Park, via an aide. These allegedly included information about ministerial candidates and North Korea.

There are even claims Ms Choi took advantage of the president's wardrobe budget - buying cheap outfits and keeping the change.

What do the two women say?

They have both apologised, but it remains unclear exactly what for.

When she was first questioned in October, Ms Choi said she had committed an "unpardonable crime", though her lawyer said this was not a legal admission of guilt.

President Park has herself admitted some lapses. She says she did consult Ms Choi for advice, and that she helped her edit her speeches, but that this stopped once she had a team of advisers in place.

Witnesses have claimed that Ms Choi received briefings and official papers long after that occurred. Documents were also discovered on an unsecured tablet computer found in an old office of Ms Choi's.

The tone of the president's pronouncements has changed over time. She began with opaque apologies: "Regardless of what the reason may be, I am sorry that the scandal has caused national concern and I humbly apologise to the people."

Image copyrightAFP

Image captionMs Park said she had "put too much faith" in her friendship with Ms Choi

But she has moved on to "heartbroken" public confessions of naivety: "Sad thoughts trouble my sleep at night. I realise that whatever I do, it will be difficult to mend the hearts of the people, and then I feel a sense of shame."

She had said she was willing to be questioned by investigators, but has so far resisted their attempts to speak to her.

Her spokesman said the prosecutors' allegation that she colluded with Ms Choi was "deeply regrettable" and "but a house of cards built on repeated imagination".

So how is Samsung involved?

Samsung's de facto head, Lee Jae-Yong, is now on trial on a string of corruption charges, including bribery and embezzlement.

Prosecutors allege Mr Lee, heir to South Korea's largest conglomerate, approved payments of 41bn won ($36m, £29m) to Ms Choi's foundations, to win government support for a big restructuring of Samsung.

He denies the allegations, as do four other Samsung executives facing trial.

Lee Jae-yong

Samsung's heir apparent

• - Grandson of Samsung founder Lee Byung-chul, son of current chairman Lee Kun-hee.
• - Also known as Jay Y Lee, the 48-year-old has spent his entire career in the company.
• - Is vice chairman of Samsung Electronics and was nominated to join the firm's board in October 2016.
• - Despite his arrest, still widely expected to take overall control of Samsung.
• - Critics say his rise through Samsung has been due to his birth, not his business experience.

Getty Images

Mr Lee, also known as Jay Y Lee, is currently vice-chairman of Samsung Electronics. But since his father, Lee Kun-hee, suffered a heart attack in 2014, he is considered de facto boss of the entire Samsung Group conglomerate.

In a December parliamentary hearing, Samsung admitted giving a total of 20.4bn won to two foundations, but denied seeking favours.

Mr Lee also confirmed the firm gave a horse and money to help the equestrian career of Ms Choi's daughter, Chung Yoo-ra, something he said he regretted.

Investigators are assessing whether the payments bought support for a controversial merger of two Samsung affiliates.

Some investors opposed the deal, saying one of the affiliates's shares were undervalued, but support from a major shareholder, the state-run National Pension Service (NPS), helped the deal go through.

The official who oversaw the NPS has since been charged with putting pressure on managers to approve the merger, which strengthened Mr Lee's control over a key part of the conglomerate.

Is anyone else involved?

Several former presidential aides have been investigated.

An Chong-bum, Ms Park's former senior secretary for policy co-ordination, has been charged with abuse of authority, coercion and attempted coercion, and Jung Ho-sung is accused of passing classified presidential documents to Ms Choi.

Local media have also been busy finding colourful associates of Ms Choi who were close to the president, including various celebrities and her personal trainer, who was appointed as a presidential aide.

Image copyrightEPA

Image captionAll the judges presiding over Ms Park's trial voted for impeachment

What now?

The impeachment verdict against Ms Park stripped her of presidential immunity.

Prosecutors then charged her with bribery, coercion, abuse of power and leaking state secrets in April 2017. Preliminary hearings in her trial began in early May.

Irfan Masih was clearing a blocked sewer in Pakistan's Sindh Province when he was overcome by toxic fumes. The 30-year-old, who is Christian, died in hospital. His family say that doctors initially refused to treat him and allege he is a victim of growing discrimination from the Muslim majority. The BBC's Riaz Sohail in Umarkot and M Ilyas Khan in Islamabad report.

When Irfan Masih was sent with two colleagues to clear a sewer that had been blocked for four months on Chhor road in Umarkot town, he could not have foreseen that his life was about to end.

His cousin Pervez, a sanitary worker like Irfan, said he was heading to work on 1 June when he heard about the incident.

"I rushed straight to the spot where some people were gathered. They had already pulled out Shaukat Masih, who was unconscious. I helped bring out Yaqoob and Irfan."

Shaukat Masih had been sent down to rescue the two. Irfan was deepest down the sewer well.

"Irfan was breathing, sometimes choking a bit. I lifted him on my shoulder and started running towards the hospital when an auto rickshaw pulled over to help me carry him.

The Taluka Headquarters Hospital in Umarkot is a small one, with only one emergency room where all three were taken. Six doctors deal with 600 outpatient and emergency cases every day.

One doctor came in, looked at Irfan and told the ward boy to clean him, Pervez Masih said. "I pleaded with him that Irfan was seriously ill and he must examine him right away. But he said he was fasting [for Ramadan], and that Irfan was covered in sewage filth. He went away."

After some time, the hospital's chief doctor arrived, he says, followed a while later by another. Neither doctor tended to the injured sanitary worker, although Pervez Masih says the second doctor told the ward boy to put him on oxygen.

"The ward boy did not wash Irfan as he was told. He continued to try to insert a cannula in Irfan's wrist but couldn't find a vein.

"All this while, I was fretting and pleading with one member of staff after another to attend to Irfan. Then I cleaned his face a bit and put my mouth on his mouth and nose and blew in to revive him.

"All this time, Irfan was breathing. Occasionally a shiver would run down his body, like someone having an epileptic fit.

"We must have been there for half an hour before he died. The last time I breathed into his mouth and nose, he pulled in a deep breath and choked a little."

It was only then that the ward boy brought the oxygen and put the mask on his mouth, he said, but there did not appear to be any oxygen in the cylinder. Minutes later a fourth doctor, Hanif Aresar, came in.

"He didn't mind the filth, just went down and embraced him and turned him on his stomach, and back on his back, and tried to resuscitate him manually. Then he said it was no use. Irfan was gone. "

Irfan was Christian, like most sanitary workers in Pakistan. Some low-caste Hindus also do the job, but Muslims avoid this work because they see it as beneath them.

Christians also face discrimination in this Muslim-majority nation. So too do Hindus, but in Umarkot there is a Hindu population of half a million, making them an influential group. There are only a small number of Christians, however, and they have no meaningful representation in the local government.

• Make up 1.6% of Pakistan's predominantly Muslim population
• Majority are descendents of those who converted from Hinduism under the British Raj
• Most converted to escape their low-caste status and many are among the poorest in Pakistan
• Targeting of Christians fuelled by strong anti-blasphemy laws and anger over US-led war in Afghanistan

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Dr Jam Kumbhar, the chief of the hospital, denies allegations that doctors refused to touch the three workers unless they were washed or that one said he was fasting (with the possible implication that he was short-tempered as a result).

He says Irfan Masih "was already dead when they brought him in," despite his cousin Pervez's detailed account of the man's last moments.

"I am a Muslim and a doctor, and part of our training is to understand that all patients are equal and we must not entertain prejudice against anyone," Dr Kumbhar told the BBC.

"I did not utter these words, nor did I hear any other doctor say that he was fasting and that he would touch the patient only after the patient was given a bath."

The BBC asked to see the entry register which lists each patient brought in to the emergency room and their medical condition. Dr Kumbhar said they couldn't find it because it had been taken away by local Christians.

Local journalist Nahid Hussain Khatak, who reached the hospital about 10 minutes after Irfan Masih, corroborates much of Pervez Masih's account.

"He had been seen by the doctors. If they thought he was dead, why would they put a cannula in his arm or give him oxygen?"

A picture taken by Pervez Masih appears to show his brother with a cannula in his arm.

Dr Kumbhar accused the Christians of turning violent.

"They were armed with sticks and were also carrying acid in bottles. They broke things at the hospital. The lives of the doctors were in danger."

The hospital administration has made a formal request to the authorities to lodge a case of terrorism against 13 members of the Christian community.

Nahid Hussain Khatak says the violence alleged "wasn't even a fraction of what the hospital administration have said".

"Someone opened the fridge in the emergency room and found it stocked with fruit (for doctors and paramedics to eat after their fast) instead of medicine, and pulled it to the ground. They smashed up a couple of tables but it was over in minutes as everybody stormed out to hold a protest."

Far from going after the Christian protesters, police are investigating the three doctors at the hospital who are accused of negligence and involuntary homicide. Dr Kumbhar was arrested and released on bail.

Pressure for a police complaint mounted when the Christian community staged their demonstration, attracting media attention.

Pervez Masih does admit he and others were angry.

"I lost my mind. Shaukat and Yaqoob were also in a serious state. So there was mayhem in the emergency room. Someone pulled down a refrigerator, a table or two were overturned, some windowpanes were broken."

But he says they left with Irfan Mashi's body when police told them to calm down.

"We took the dead body straight to the town square where we staged a sit-in for seven hours, and left only after the district administration high-ups assured us that justice would be done."

It was this anger, he believes, that convinced police to lodge a complaint against the three doctors, and that convinced the hospital staff to immediately arrange to transfer the two other Christian men to hospitals in Hyderabad and then Karachi.

"Shaukat has revived, but Yaqoob is still in a serious condition," Pervez says.

Locals say at least two other Christian sanitary workers lost their lives cleaning the same sewer three years ago.

Mir Hasan Aresar, a columnist and social worker, says there have been examples of intolerance towards minorities in this area. "Tolerance is diminishing, and it's worrying," he said.

The government has announced compensation of a million rupees ($15,000, £12,200) to the family of Irfan Masih, but his mother, Arshad Bibi, is not content.

"I want justice. I want the doctors to be punished so that this doesn't happen to another poor family."

His father, Nazeer, said the first doctor did discriminate against Irfan and the others.

"He said he was fasting, and the patients were dirty. His clothes would get soiled, he said. He asked us to wash the patients before he could treat them.

"They hate us. They don't allow us to sit next to them because we are sweepers. The politicians came here because the case was highlighted in the media. Otherwise, no-one bothers."