Beirut — The bodies of at least 67 Syrian civilians, many summarily killed by the Islamic State group, have been discovered in a central town in Syria retaken from ISIS by government troops over the weekend, activists said on Monday.The news of the gruesome find in the town of Qaryatayn, in Homs province, began to emerge first late on Sunday. The number of bodies was likely to climb.Some were shot in the street as ISIS militants retreated from the town, gunned down because they were suspected of working with the governments, according to activists. At least 35 of the casualties were found shot and their bodies dumped in a shaft.The Britain-based Syrian Observatory for Human Rights said it had documented the killings of at least 128 people killed in Qaryatayn during the last days of ISIS control of the town.On Saturday, Syrian troops and allied militias regained control of the town, which was held by ISIS for three weeks.The government-run Syrian Central Military Media at the time said the Syrian army and its allies restored security and stability to Qaryatayn after clearing the town of ISIS fighters.The head of the Observatory, Rami Abdurrahman, said that what happened in the town was a "massacre".The activist-run Palmyra Co-ordination 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.'Sleeper cells'The activist-run group said other bodies were also found in the town streets — apparently of people shot by pro-government forces and suspected of working with ISIS. The Observatory also said it documented at least 12 killed at the hands of pro-government troops after they regained control of the town.ISIS militants first seized Qaryatayn in August 2015, and relied on the strategically located town to defend another of their bastions, the historic city of Palmyra.At the time, thousands of the town's Christian residents fled, fearing the extremist group's brutality.With Russian backing, Syrian troops regained control of the town in April 2016. But ISIS, facing major setbacks around Syria and Iraq, launched a new attack on the town in late September and recaptured it.At the time, Russia accused the United States, which is battling the Islamic State group, of looking the other way and allowing ISIS to attack Qaryatayn.Most of the ISIS militants who were involved in attacks on the town were local residents. Pro-government media blamed the loss of Qaryatayn for the second time on what it described as militant "sleeper cells".There was no immediate comment from the government in Damascus on the find of the civilian bodies in Qaryatayn.