The military action is taking place after Russian President Vladimir Putin and Iranian President Masoud Pezeshkian expressed their “unconditional support” for the Syrian government.

Syria’s military has said its joint airstrikes with Russia have killed at least 400 insurgents over the past 24 hours – as Vladimir Putin reaffirmed his support for Syrian President Bashar al Assad.

The strikes are being carried out after insurgents led by jihadi group Hayat Tahrir al Sham and including Turkey-backed fighters launched a two-pronged attack on Aleppo, Syria’s second largest city, on Saturday.

The rebels then moved into the countryside around the provinces of Idlib and neighbouring Hama.

Syrian and Russian airstrikes have mainly been carried out on rebel positions in those two provinces, Syria’s military said.

Syria’s opposition-run White Helmets rescue service said on Monday that at least 25 people, including 10 children, have been killed in airstrikes carried out by the Syrian government and Russia.

It comes as Mr Putin and Iranian President Masoud Pezeshkian spoke in a phone call about the “escalating situation” in Syria, the Kremlin said.

The pair, who are both longtime allies of the Syrian president, discussed “large-scale aggression” by rebel fighters which they viewed “as an attempt to undermine the sovereignty, political, and socio-economic stability of the Syrian state”, a statement read.