A war monitor said Monday that air raids in Syria the previous night, blamed on Israel, killed at least three foreign pro-regime fighters south of the war-torn country's capital. 

Tens of thousands of civilians are fleeing bombardment in Syria's Idlib region, the UN said, as fighting flares in the jihadist bastion fuelling an already dire humanitarian situation.

The Idlib region, which is home to some three million people including many displaced by Syria's civil war, is controlled by the country's former Al-Qaeda affiliate, Hayat Tahrir al-Sham. The Damascus regime has repeatedly vowed to take back control of it.

Syrian regime air strikes and artillery fire on Tuesday killed 23 civilians in the last major opposition bastion in the northwest of the country, a war monitor said.

The value of the Syrian pound on the black market sank to 1,000 to the dollar at some money changers Tuesday, marking a new record low for the nosediving currency.

Regime air strikes Monday killed 10 civilians in Syria's last major opposition bastion, where deadly clashes between regime forces and armed groups have escalated in the past two days, a monitor said.

Syria's President Bashar al-Assad on Thursday approved a $9.2-billion budget for his war-torn country, official media reported.

Russia has begun moving helicopters and other equipment to a new Syrian base on the Turkish border, state TV reported on Thursday, weeks after US forces left the area.

Two Mi-35 attack helicopters and a transport helicopter were moved from the Hmeimim base on the Mediterranean to Qamishli airport in northeastern Syria, reported Zvezda television, which is run by the defence ministry.

The United States will maintain around 600 troops in Syria, Pentagon chief Mark Esper said Wednesday, despite Donald Trump's desire to end US involvement in what the president calls "endless wars".

Eleven pro-Turkish Syrian fighters were killed Thursday by Kurdish forces in violation of ceasefire agreements aimed at creating a "safe zone" in northern Syria, Turkey's President Recep Tayyip Erdogan said.

Some 300 Russian military police have arrived in Syria to patrol the flashpoint Syrian-Turkish frontier, the defence ministry said on Friday.