Activists say some 100 soldiers, guards and employees were killed when jihadis seized a gas field in central Syria on Thursday.
An activist in the central province of Homs, who goes by the name Beibares Tellawi, said Friday that militants from the Islamic State group attacked army checkpoints and seized the Shaer gas field in the desert region of Palmyra the day before.
The Britain-based Syrian Observatory for Human Rights said 115 people were killed. The Syrian government has not commented and an official in Homs said he had no information on the incident.
The Observatory and Tellawi said the field fell to the militants Thursday night after a day of clashes.
The Islamic State group has already captured much of the oil-rich eastern province of Deir el-Zour.