Islamic State killed 116 civilians over 20 days while the militia was in control of the central Syrian town of al-Qaryatayn, the Syrian Observatory for Human Rights said Monday.
More than 80 of those killed are believed to have been executed in the two days before Islamic State left al-Qaryatayn on October 20 as government forces regained control of the town, Observatory head Rami Abdel Rahman said.
The civilians were killed on charges of collaborating with the regime.
Government forces are fighting to dislodge Islamic State militants from Syria’s eastern Deir al-Zour province, the largest area controlled by the jihadist group in the country after rebels liberated the northern al-Raqqa province last week.
On October 1, Islamic State militants managed to infiltrate the town of al-Qaryatayn, which was under government control. The town is located in the south-eastern part of the central province of Homs.
In a counter-attack, the regime on Friday managed to retake the town.
Abdel Rahman said that 12 other civilians were also killed by the regime when they took back al-Qaryatayn.
“We have been able to document more than 170 people killed. There are dozens of missing people and more than 30 bodies were found on Sunday evening in two wells near the city,” Mohammed Arandas, head of the local council of the town, who currently lives in Turkey, told dpa.
Arandas expects new mass graves to be uncovered in the coming days.
The state-run SANA news agency posted pictures inside al-Qaryatayn, which showed mainly empty streets and some damaged Islamic State military vehicles.
The Observatory said around 200 militants were in town and withdrew towards the desert areas in the eastern part of the province of Homs, adjacent to Deir al-Zour.
On Monday, the Observatory said that heavy battles are ongoing between government forces and Islamic State militants at the frontlines in the south-eastern desert of Deir al-Zour near the administrative border with the province of Homs.
Islamic State is still active in these desert areas, where its militants have recently carried out a string of counter-attacks in an attempt to regain its lost territory in Syria.