IS advances on regime-held airbase in eastern Syria

Fighters of the Islamic State group (IS) edged closer to a strategic airbase in eastern Syria in heavy fighting that left more than 41 combatants dead, a monitoring group said on Thursday.

The extremist group, which has captured territory across Iraq and Syria, seized control late Wednesday of a small base near the regime-held military airport outside Deir ez-Zor, the Syrian Observatory for Human Rights said.

"It was one of the Islamic State's fiercest attacks on the airport. Eighteen regime soldiers and 23 Daesh fighters were killed," Observatory director Rami Abdel Rahman said, using an Arabic acronym for the jihadist group.

The seizure of the small base, used by the army's rocket battalion, brings IS within little more than a kilometre of the airport.

Abdel Rahman said IS fighters had used two suicide bombers in the assault, one of them a child, driving cars laden with explosives.

More than 50 jihadists were wounded in the fighting, he added.

IS fighters used two suicide bombers in the assault, one of them a child, driving cars laden with explosives - Rami Abdel Rahman

The IS already controls most of oil-rich Deir ez-Zor province including roughly half of its capital, and has attempted to capture the airport and the rest of the city for more than a year.

If IS succeeds, Deir ez-Zor would be the second provincial capital to fall to the group after the northern city of Raqqa, which it named the capital of its "caliphate."

At least 56 regime soldiers die in fall of Abu Zuhour air base

The assault came as rival jihadists of al-Qaeda-affiliated Nusra Front and their allies seized Abu Zuhour air base, the last regime-held military base in Idlib province in the northwest of the country on Thursday.

"There were at least 56 (soldiers) killed yesterday and at least 40 taken prisoner, and dozens more are missing," Rami Abdel Rahman, from the the Syrian Observatory for Human Rights, said.

"Some soldiers were executed," said the head of the Britain-based group that relies on a network of sources on the ground in Syria for its information.

Dozens of others were either taken prisoner or went missing when Nusra and a coalition of mostly Islamist groups captured the Abu Zuhour military airport on Wednesday, the Syrian Observatory for Human Rights said.

Nusra posted pictures on Twitter of about 15 men it said were Syrian soldiers now "in the hands of the mujahedeen".

Rebels also uploaded images of helicopters and planes abandoned on the tarmac, with militants posing seated on one of the aircraft making V-for-victory signs.

The fate of other missing soldiers remained unclear, said Abdel Rahman, who added that the entire northwestern province of Idlib was under the control of Nusra and other rebel groups.

The insurgents took advantage of an intense sandstorm that blanketed much of the Middle East on Tuesday evening to seize the airbase, the observatory said.

Assad's regime effectively acknowledged the loss, with state television saying troops had left the base.

According to the Observatory, the regime is now left with just three airbases in the east and north - Deir Ezzor, and Neirab and Kweyris in Aleppo province.