The Syrian Observatory for Human Rights said on Monday Islamic State killed at least 128 people in the Syrian town of al-Qaryatayn 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.
Syrian activists reported that at least 65 bodies have been found in Qaryatayn, a central town in Homs retaken by government forces from ISIS. Most of the victims are believed to have been killed by ISIS.
The Britain-based Syrian Observatory for Human Rights says most of the dead were killed during the militant group's three-week seizure of the town.
Syrian troops and allied fighters regained control of the town on Saturday.
The activist-run Palmyra Coordination Committee has published the names of the killed. It says at least 35 of the victims were found shot and their bodies dumped in a shaft.
ISIS has suffered major setbacks in recent months.
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