The Assad regime insists that it is still in control of the airport in Deir Ez Zor, while the Islamic State of Iraq and the Levant group controls much of the rest of the province.
Kurdish forces in the Syrian town of Kobane say they have made advances against ISIL fighters.
Also on Sunday, intense fighting took place in the province of Aleppo. Rebel fighters said they killed several soldiers in the village of al-Mallah and destroyed some military vehicles.
But the Syrian state news agency, quoting a military source, said that the government remains in control of the village.
Al Jazeera’s Bernard Smith reports from Istanbul.