LATEST: Video — Car Bomb in Damascus Suburb of Douma

Uncertainty continued on Friday over one of the largest mass killings in the 40-month Syrian conflict — carried out not by the Assad regime but by the jihadist Islamic State as it took over a gas field in central Syria.

The Islamic State seized the al-Sha’er field in the Palmyra region on Thursday. It boasted of the takeover in a graphic video showing its fighters striking bodies with shoes.

Initial reports said 23 guards were killed in the field, but an activist linked to the Islamic State said “dozens” of defenders had died while 12 jihadists had been slain during their attack.

Subsequent, unconfirmed claims assert far more of the 340 employees of the plant were killed, with one claim reaching 270 killed in fighting or subsequently executed.

The Governor of Homs Province, Talal Barazi, said on Thursday that Syrian forces were trying to recapture the field, but this has been followed by silence from State media. A “monitoring group” asserted that regime troops had killed 40 jihadists on Friday.

The Islamic State has already taken over Syria’s largest oilfields as it defeated insurgents in the east of the country. The latest advance raises the prospect of direct conflict with the Assad regime, which has largely refrained from attacks on the jihadists as they have inflicted losses on the insurgency — reports on Friday indicated that the regime was securing an oilfield near al-Sha’er.

Video: Car Bomb in Damascus Suburb of Douma

Aftermath of a car bomb on Saturday in the Damascus suburb of Douma — multiple casualties are reported: