Beirut - Jihadists killed at least 90 Syrian regime fighters, civilian security guards and employees when they seized a gas field in Homs province, a monitoring group said on Friday.
The Syrian Observatory for Human Rights described on Thursday's takeover of the Shaar field as "the biggest" anti-regime operation by the Islamic State (IS) since it emerged in the Syrian conflict last year.
"At least 90 people, mainly security guards and members of the [paramilitary] National Defence Forces in the IS attack on the Shaar gas field in Homs province", Observatory director Rami Abdel Rahman said.
"Twenty-five of the killed were civilian employees", he told AFP.
"The rest were security guards deployed by the oil ministry and members of the National Defence Force."
Footage apparently shot by the jihadists at the gas field and distributed via YouTube showed dozens of bodies, some of them mutilated, strewn across the desert landscape.
One video shows a jihadist posing with the bodies as he speaks in German interspersed with religious terms in Arabic, seemingly celebrating the killings.
The Islamic State, which proclaimed a "caliphate" straddling Syria and Iraq last month, has also taken over Syria's oil-rich Deir Ezzor province.
Deir Ezzor borders Homs province as well as Iraq, where the jihadist group has spearheaded a major Sunni militant offensive that has seen large swathes of territory fall out of the Baghdad government's control.