The United Nations said Tuesday that a Somali stoned to death by Islamist militants after she had been accused of adultery was a 13-year-old girl who had been raped while visiting her grandmother.

In the first such public killing by the militants in about two years, she was placed in a hole and stoned to death on Oct. 28 in a rebel-held port city, Kismayu, in front of a crowd, after local leaders said she was guilty under Shariah, the legal code of Islam based on the Koran.

“Reports indicate that she had been raped by three men while traveling on foot to visit her grandmother in the war-torn capital, Mogadishu,” Unicef, the United Nations children’s agency, said in a statement.

“Following the assault, she sought protection from the authorities, who then accused her of adultery and sentenced her to death,” Unicef added. “A child was victimized twice — first by the perpetrators of the rape and then by those responsible for administering justice.”

The human rights group Amnesty International has identified the girl as Aisha Ibrahim Duhulow and said she was killed by 50 men who stoned her in a stadium in Kismayu in front of about 1,000 spectators.

When the family tried to report the rape to the Shabab militia that controls Kismayu, the girl was accused of adultery and was detained. None of the men she accused of rape have been arrested.

A Somali news agency adds more disturbing details:

Thousands of people witnessed the grotesque execution of Aisha at a football stadium in the port town of Kismayo on Monday.

The 13-year old was led in and forced into a hole in the ground. The hole was then filled so that only her head was showing. About 50 men then started to throw stones at her, according to Amnesty’s information.

After a while, nurses were called to check whether Aisha was still alive. The thin body was then brought out of the hold and examined. When it was established that she was still alive, she was again placed in the hole so that the stone-throwers could continue.

When some of the spectators tried to storm the stadium to save Aisha, the militia opened fire on the crowd, and a young boy was killed.

A spokesman for the Shabab-militia expressed regret for the boy’s death and assured that the soldiers who had opened fire would be punished.

However, it would seem that the men whom13-year old Aisha tried to report for rape have little to fear. None of them have been arrested.