The Britain-based Syrian Observatory for Human Rights says the latest attack began today with a suicide car bomb attack on the main entrance of the Deir el-Zour air base.
The Islamic State group began a major offensive on the air base, one of the last government-held areas in the province of Deir el-Zour, on Thursday.
Activists who support the Islamic State group posted photos on social media showing two military helicopters that they claimed were captured by the jihadis.