BEIRUT — The Syrian Observatory for Human Rights said on Monday that Daesh (the so-called IS) killed at least 128 people in a Syrian town in central Homs over a three-week period before the Syrian army recaptured it on Saturday.

There was no immediate comment from Syrian government officials or state media on the report by the Observatory, a Britain-based war monitor.

Syrian troops and allied forces regained control of Al-Qaryatain town "after eliminating terrorist Daesh groups that had infiltrated it," state media said on Saturday.

Earlier this month, the Observatory said IS fighters had seized the town from government forces, part of a counter-attack by the jihadists who have come under intense pressure in eastern Syria.

At least 83 people were killed in the 48 hours before the Syrian army retook the town, the war monitor said, adding that IS had accused the civilians of being "agents of the regime".

The town lies nearly 300 km (190 miles) from Deir Al-Zor city in the east, the current focus of the government offensive.

"IS has over a period of 20 days executed at least 116 civilians in reprisal killings, accusing them of collaboration with regime forces," said Rami Abdel Rahman, head of the Britain-based Syrian Observatory for Human Rights monitor.

"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.

Rami Abdel Rahman sad that what happened in the town was a "massacre."

The activist-run Palmyra Coordination Committee published the names of 67 civilians confirmed killed and also said the number was likely to rise. It said at least 35 were found shot and dumped into a deep shaft.

The Observatory also said it documented at least 12 killed at the hands of pro-government troops after they regained control of the town. — Agencies