Report: ISIS massacred 116 people in Christian town in Syria before government troops closed in

The Islamic State has reportedly executed at least 116 residents of a Christian town in Syria before the terror group was driven out by government troops.

According to the U.K.-based monitoring group Syrian Observatory for Human Rights (SOHR), ISIS militants carried out the executions in the Christian desert town of Al-Qaryatain just days before it was recaptured by Syrian government troops.

"ISIS has over a period of 20 days executed at least 116 civilians in reprisal killings, accusing them of collaboration with regime forces," SOHR chief Rami Abdelrahman said.

Newsweek reported that the town came under the control of ISIS three weeks ago. But the militant group retreated after Syrian regime forces, backed by Russian air power, arrived and recaptured the town on Oct. 21. After liberating the town, the government troops found the remains of the victims of the mass execution.

"After the regime retook it, the town's residents found the bodies on the streets. They had been shot dead or executed with knives," Abdelrahman said.

"Most of the ISIS 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 went on to say.

Talal Barazi, the governor of Homs province, told Associated Press on Monday that the victims were townspeople who were mostly government employees or were affiliated with Syria's ruling Baath party.

He described the incident as a "shocking massacre," noting that the executions went on for the three weeks that the militant group had control of the town, which lies some 100 kilometers southwest of the ancient city of Palmyra.

Government forces are reportedly continuing the search for victims in the town. Another activist group, known as the Palmyra Coordination Committee, had identified the bodies of 67 civilians and noted that the figures could still increase.

ISIS initially captured the town in August 2015 but was forced out in April 2016. At the time, the militant group destroyed the Christian monastery of Mar Elian and took hundreds of Christians captive.

The Christians were reportedly forced to live under the militant group's ultraconservative brand of Islamic rule and were only returned to their homes after they agreed to pay jizya (tax) and sign a dhimma (a Sharia social contract) in order to remain in the town and not face death.

A copy of the dhimma obtained by SOHR in 2015 showed that the orders came from ISIS's caliph, Abu Bakr al-Baghdadi. It stated that al-Baghdadi "gives" the Christians a guarantee on their "money, souls, not to force them to change their religion and not to harm any one of them."