IS 'executed' 116 in Syria town revenge campaign
More than 100 people were massacred in the desert town of al-Qaryatain before they lost it to regime forces this month, the Syrian Observatory for Human Rights, a Britain-based monitor, said.
"IS has over a period of 20 days executed at least 116 civilians in reprisal killings, accusing them of collaboration with regime forces," Observatory chief Rami Abdel Rahman said.
Regime forces retook al-Qaryatain, which lies in the central Homs province, on Saturday, three weeks after the militants had seized control of it.
On Monday, state news agency SANA published footage from inside the town, showing a ransacked and partially burnt hospital, and roads with rubble strewn across them.
Homs governor Talal Barazai greeted residents, thanking them for their "steadfastness", and pledging to stand by them, as dozens of people queued to receive aid being distributed by the Syrian Arab Red Crescent.
IS first occupied the town in 2015 and lost it to Russian-backed Syrian forces last year.
"After the regime retook it (on Saturday), the town's residents found the bodies on the streets. They had been shot dead or executed with knives," Abdel Rahman said.
"Most of the IS fighters who attacked the town a month ago were sleeper cells... They are from the town, know the town's residents and who is for or against the regime," he said.
The majority of those killed were executed in the last two days before IS lost the town again, he added.
The regime seized back al-Qaryatain on Saturday after more than 200 militants withdrew overnight, pulling back into the vast desert region that stretches all the way to the Iraqi border.
Al-Qaryatain was a symbol of religious coexistence before Syria's civil war broke out in 2011, with some 900 Christians among its population of 30,000.
But it was ravaged by IS during the group's eight-month-long occupation of the town in 2015-16, with its Christian sites including a fifth-century church reduced to rubble.
Last week, the extremist group lost its key Syrian stronghold of Raqqa, the latest in a string of setbacks for the militants who are facing multiple offensives in both Syria and neighbouring Iraq.
At the peak of its power in 2014, IS' self-styled "caliphate" in Syria and Iraq was approximately the size of Britain.
But it has suffered a string of major setbacks in recent months, including the loss in July of its most important Iraqi stronghold, the city of Mosul.
The militant group is now mostly confined to the oil-rich province of Deir az-Zour in Syria's east, along the border with Iraq.
IS holds around 40 percent of the province, which was once almost completely in its hands, and faces two separate offensives, including by the SDF.
The US-backed Arab-Kurdish alliance is fighting the group mostly on the eastern side of the Euphrates River that slices diagonally across the province.
On Sunday, SDF fighters seized one of the country's largest oilfields from the group.
Syria's regime is conducting a separate, Russian-backed offensive in the province, largely on the western bank of the river.
In September, the offensive ended an IS siege of nearly three years on government-held parts of the provincial capital Deir az-Zour city.
The group now holds just eight percent of the city, according to the Observatory.
Elsewhere in Syria, IS holds just a few pockets of territory, including a handful of recently recaptured villages in central Hama province, and parts of the Palestinian camp of Yarmouk in southern Damascus.
An allied group, Jaish Khaled Bin Walid, is also present in parts of southern Syria.
Agencies contributed to this report.