A young woman recently stoned to death in Somalia first pleaded for her life, a witness has told the BBC.

"Don't kill me, don't kill me," she said, according to the man who wanted to remain anonymous. A few minutes later, more than 50 men threw stones.

Human rights group Amnesty International says the victim was a 13-year-old girl who had been raped.

Initial reports had said she was a 23-year-old woman who had confessed to adultery before a Sharia court.

The witness says she was forced into a hole, buried up to her neck then pelted with stones until she died in front of more than 1,000 people.

Cameras were banned from the public stoning, but print and radio journalists who were allowed to attend estimated that the woman, Aisha Ibrahim Duhulow, was 23 years old.

However, Amnesty said it had learned she was 13, and that her father had said she was raped by three men.

People were saying this was not good for Sharia law, this was not good for human rights, this was not good for anything Witness

When the family tried to report the rape, the girl was accused of adultery and detained, Amnesty said.

Convicting a girl of 13 for adultery would be illegal under Islamic law.

A human rights activist in the town told the BBC on condition of anonymity that he had received death threats from the Islamic militia, who accuse him of spreading false information about the incident.

He denies having anything to with Amnesty's report.

'Checked by nurses'

Court authorities have said the woman came to them admitting her guilt.

She was asked several times to review her confession but she stressed that she wanted Sharia law and the deserved punishment to apply, they said.

But a witness who spoke to the BBC's Today programme said she had been crying and had to be forced into a hole before the stoning, reported to have taken place in a football stadium.

"More than 1,000 people arrived there," he said.

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"After two hours, the Islamic administration in Kismayo brought the lady to the place and when she came out she said: 'What do you want from me?'"

"They said: 'We will do what Allah has instructed us'. She said: 'I'm not going, I'm not going. Don't kill me, don't kill me.'

"A few minutes later more than 50 men tried to stone her."

The witness said people crowding round to see the execution said it was "awful".

"People were saying this was not good for Sharia law, this was not good for human rights, this was not good for anything."

But no-one tried to stop the Islamist officials, who were armed, the witness said. He said one boy was shot in the confusion.

According to Amnesty International, nurses were sent to check during the stoning whether the victim was still alive. They removed her from the ground and declared that she was, before she was replaced so the stoning could continue.

The port of Kismayo was seized in August by a coalition of forces loyal to rebel leader Hassan Turki, and al-Shabab, the country's main radical Islamist insurgent organisation.

Mr Turki is on the US list of "financers of terrorism".

It was the first reported execution by stoning in the southern port city since Islamist insurgents captured it.

The BBC had a reporter in the area, but he was shot dead in Kismayo in June.