Syrian troops and militia backed by Russian jets mounted what appeared to be their first major coordinated assaults on Syrian insurgents yesterday and Moscow said its warships fired a barrage of missiles at them from the Caspian Sea, a sign of its new military reach.

The combined assault hit towns close to the main north-south highway that runs through major cities in the mainly government-held west of Syria, said the Syrian Observatory for Human Rights, which tracks the conflict via a network of sources within the country.

Ground attacks by Syrian government forces and their militia allies using heavy surface-to-surface missile bombardments hit at least four insurgent positions and there were heavy clashes, the head of the Observatory, Rami Abdulrahman, said. The Iranian-backed Hizbollah militia took part in the fighting, a regional source said.

Islamic State militants have seized much of Syria since civil war grew out of anti-government protests in 2011, but the areas targeted in yesterday’s combined assault are held by other rebels, some US–backed, fuelling allegations by Russia’s critics that its real aim is to help the government.

Iraq may also request Russian aid

Russian Defence Minister Sergei Shoigu told President Vladimir Putin during a televised meeting that four Russian warships in the Caspian Sea had launched 26 missiles at Islamic State in Syria earlier in the day. The missiles would have passed over Iran and Iraq to reach their targets, covering a distance of almost 1,500 km, the latest display of Russian military power at a time when relations with the West are at a post-Cold War low over Ukraine.

The terrain-hugging Kalibr cruise missiles, known by Nato by the codename Sizzler, fly at an altitude of 50 metres and are accurate to within three metres, the Russian defence ministry said.

The air campaign in Syria has caught Washington and its allies on the back foot and alarmed Turkey, which says its airspace has been repeatedly violated by Russian jets. Ankara summoned Russia’s ambassador for the third time in four days over reported violations, which Nato has said appeared to be deliberate and were “extremely dangerous”. Turkey said Syria-based missile systems harassed its warplanes on Tuesday while eight F-16 jets were on patrol along the Syria border.

Russian air strikes destroyed the main weapons depots of a US-trained rebel group, the Liwa Suqour al-Jabal, their commander said. But in Iraq, the head of Parliament’s defence and security committee said Baghdad may request Russian air strikes against Islamic State on its soil soon and wants Moscow to have a bigger role than Washington in fighting the group.

Iraq’s government questions the United States’ resolve in fighting IS militants, who control a third of the country, saying US-led coalition air strikes are ineffective.