BEIRUT: A preacher read the verdict before the truck came and dumped a large pile of stones near the municipal garden. Jihadi fighters then brought in the woman, clad head to toe in black, and put her in a small hole in the ground. When residents gathered, the fighters told them to carry out the sentence: Stoning to death for the alleged adulteress.

None in the crowd stepped forward, said a witness to the event in a northern Syrian city. So the jihadi fighters, mostly foreign extremists, did it themselves, pelting Faddah Ahmad with stones until her body was dragged away.

"Even when she was hit with stones she did not scream or move," said an opposition activist who said he witnessed the stoning near the football stadium and the Bajaa garden in the city of Raqqa, the main Syrian stronghold of the Islamic State group.

The July 18 stoning was the second in a span of 24 hours. A day earlier, 26-year-old Shamseh Abdullah was killed in a similar way in the nearby town of Tabqa by Islamic State fighters. Both were accused of having sex outside marriage.

The killings were the first of their kind in rebel-held northern Syria, where jihadis from the Islamic State group have seized large swaths of territory, terrorizing residents with their strict interpretation of Islamic law, including beheadings and cutting off the hands of thieves. The jihadis recently tied a 14-year-old boy to a crosslike structure and left him for several hours in the scorching summer sun before bringing him down - punishment for not fasting during the Muslim holy month of Ramadan.

The group has also brutalized Shiites and others whom it views as apostates. In neighboring Iraq, Islamic State militants have driven members of the Yazidi religious minority out of a string of towns and villages. Thousands of the fleeing Yazidis have been stranded on a mountaintop for days, a humanitarian crisis that prompted the U.S. to airlift aid to them this week.

On Friday, Kamil Amin, the spokesman for Iraq's Human Rights Ministry, said hundreds of Yazidi women under the age of 35 are being held by the Islamic State group in schools in Iraq's second largest city Mosul, which the militants captured in June.

The stonings in Syria last month were not widely publicized at the time, but in the following days three photographs appeared online which appeared to document the grisly spectacle and were consistent with other AP reporting.

The pictures posted on a newly-created Twitter account showed dozens of people gathered in a square, a preacher reading a verdict through a loudspeaker and several bearded men with automatic rifles either carrying or collecting stones.

"A married woman being stoned in the presence of some believers," read the caption of the photographs on the Twitter account, which has since been suspended.

Abu Ibrahim Raqqawi, the activist who witnessed Ahmad's stoning, said locals where angry to see foreign fighters impose their will on the community.

"People were shocked and couldn't understand what was going on. Many were disturbed by the idea that Saudis and Tunisians were issuing (such) orders," he said in an interview via Skype. Ahmad, he said, appeared unconscious, and he had overheard that she was earlier taken to a hospital where she was given anesthesia.

The stoning took place after dark, he said, at about 11 p.m. He could not see blood on the body because of the black clothes she was wearing. Ahmad did not scream or shake, and died silently. "They then took the dead body in one of their cars and left," he said.

The two cases were first reported by the Britain-based Syrian Observatory for Human Rights, which collects information through a network of activists around the country. Bassam Al-Ahmad, a spokesman for the Violations Documentation Center, a Syrian group that tracks human rights violations, also confirmed the stoning.

An activist based in the northern province of Idlib, who collects information from other activists in northern Syria, said Ahmad was a widow. A man who asked to be identified as Asad for fear of repercussions, said that in the other stoning, in Tabqa, residents also refused to take part, and that the act was carried out by Islamic State members.

The U.S. Embassy in Syria, in a statement posted on its Twitter account, condemned the "barbaric stoning" of a woman in Tabqa.

International human rights groups did not report the stoning, and Human Rights Watch said it had no independent confirmation.

"It is a very worrying trend if true," said Human Rights Watch researcher Lama Fakih.

The Islamic State group has "imposed incredibly restrictive rules on the civilian population which have served to make women and girls particularly vulnerable and to quite clearly discriminate against them," she said, adding that the reports of the stoning were the first the group had received out of Syria.

"This is just a more sort of extreme manifestation of those restrictive rules which are all in violation of international" human rights law, she said.

Such acts have alarmed members of mainstream Syrian opposition groups fighting to remove President Bashar Assad from power since 2011.

"These behaviors have nothing to do with the nature and mentality of Syrian society," said Abdelbaset Sieda, a senior member of the main Western-backed Syrian National Coalition. He said the group had no official confirmation of the stoning cases although he did not rule it out. "We expect such acts to be carried out by the Islamic State," he said.

The Hazm Movement, another rebel group active in northern Syria, said the stonings did take place. It added that such acts "contradict the principals of the revolution" and encourage the world to refrain from giving any support to the rebels.

"The world should know that every day they delay real support to active moderate groups is direct support to extremist factions," the group said in response to written questions from The Associated Press.