The Syrian Observatory for Human Rights announced Saturday that bombardment and gassing ended a push to take a military air base (pictured) by the "Islamic State" (IS).

IS began its offensive to capture the base, from which troops have launched air attacks - as well as a nearby barracks known as Brigade 137 - on Thursday. Deir al-Zour lies in the northeast, between the IS-controlled province of Raqqa and the Iraqi border.

"Our brave troops managed to hit an Islamic State convoy near the Deir al-Zour military airport," Syria's state broadcaster reported Saturday, without giving further detail.

Losing Deir al-Zour would prove a major blow for Assad's regime, making it the second Syrian province after Raqqa to fall into the hands of IS, which also controls considerable swaths of territory in Iraq. The battle for the air base and the region has killed about 70 IS fighters and 51 regime troops in the past three days, according to the Observatory, which is based in Britain and relies on reports from activists within Syria, where few unofficial media have a presence.

The dead IS fighters included two French citizens. The news of the deaths follows much hand-wringing in the European Union over what to do with citizens who return after fighting for IS. On Friday, the United Kingdom convicted two men of helping plan terrorist attacks in Syria, and Germany also put a returned IS fighter in prison.

‘Fierce clashes'

By Friday, IS had captured the strategic village of Jafra near the air base. Saturday's attacks began with a suicide car bomb at the main entrance of the Deir el-Zour air base.

IS fighters then began storming the airbase in a bid to take full control of the oil-rich region. Rami Abdel-Rahman, the head of the Syrian Observatory for Human Rights, told the German news agency dpa on Saturday that IS had already captured parts of the eastern side of the air base, including a missile facility.

The group's supporters posted photos showing two military helicopters that they claimed the group had captured from the government. Despite state media's quickness to report the government's successes, the national broadcaster made no mention of Saturday's capture of parts of the air base or the helicopters.

The US-led coalition against IS does not officially coordinate its own airstrikes with Assad, who has few supporters in the region and elsewhere, but that has not stopped the group from launching attacks on government forces and even rival rebel factions fighting to oust Syria's autocrat. Late Friday, the US Embassy in Syria announced that an airstrike in Deir al-Zour had hit IS targets: three vehicles, an excavator and a training camp. It remained unclear whether the attacks had taken place near the base.

On Friday, Amnesty International released a report accusing weatlhy nations of doing little to help Syrians other than militarily.

mkg/rc (Reuters, AFP, dpa, AP)