The Russian military claims to be bombing Syrian anti-government troops.

Russia’s military said Friday its air force had bombed anti-government forces in Syria to repel opposition fighters that have launched a major offensive on the city of Aleppo, Russian state news agencies reported.

Opposition and their Turkish-backed allies reached Syria’s second city on Friday, pressing a lightning offensive against forces of the Iranian- and Russian-backed government.

The fighting is some of the deadliest in years in Syria’s civil war.

“The Russian air force is carrying out rocket-bomb attacks on the equipment and manpower of illegal armed groups, control points, warehouses and artillery positions of terrorists,” news agencies reported a spokesperson for the defence ministry’s Reconciliation Center for Syria as saying.

It claimed that 200 militants had been “destroyed” over the last 24 hours.

AFP could not verify that figure.

“The operation to repel the aggression of the extremists continues,” said Oleg Ignasyuk, deputy head of the Russian reconciliation centre, state media reported.

Moscow is Syrian leader Bashar al-Assad’s most important military backer, having turned the tide of the civil war in his favour when it intervened in 2015.