Updated

Syrian activists say government warplanes have carried out at least eight strikes against Islamic State militants attacking a key military air base in eastern Syria.

The Local Coordination Committees, an activist collective, and the Britain-based Syrian Observatory for Human Rights say the airstrikes took place Sunday on four areas near the airfield, which is just outside the city of Deir el-Zour.

The Islamic State group launched its assault on the facility last week, touching off fighting that activists say has killed more than 150 people on both sides.

For IS, seizing control of the base would eliminate the last significant government presence in the area and provide a major moral and propaganda boost.