BEIRUT (TheBlaze/AP) — Islamic State militants on Saturday killed dozens of people, most of them pro-government militiamen, in wide-scale attacks on government-held areas of the eastern city of Deir el-Zour, opposition activists said.

AP Photo

Islamic State flag (AP photo)

The opposition activist group the Syrian Observatory for Human Rights said at least 135 people were killed, at least 80 of them soldiers and pro-government militiamen and the rest civilians, in the attacks which saw the group make significant advances in the contested city.

The Islamic State group controls most of the province and provincial capital with the same name, while the government controls a few neighborhoods in the northern part of the city and the adjacent military airport. Most of the casualties took place in the area of Baghaliyeh near the northern tip of the city.

The state news agency SANA said Islamic State militants committed “a massacre,” killing dozens of civilians in Baghaliyeh village. It did not elaborate. The Lebanon-based Al-Mayadeen TV, which is close to the Syrian government, also reported a massacre and said the Islamic State killed 280 people, including women and children, and threw their bodies in the Euphrates River. It said the group took more than 400 civilians hostage.

The reports could not be independently confirmed.

The Islamic State-affiliated Aamaq news agency had reported a large-scale multi-pronged attack on Deir el-Zour that began with a suicide bombing. Opposition activists said Russian warplanes were carrying out intensive airstrikes in support of government forces in the area.

This story has been updated.