Moscow is Syrian leader Bashar al-Assad's key supporter, providing him with military, political and economic support throughout the country's decade-long civil war.

"On November 11, Russia's aerospace forces carried out air strikes in Idlib province against sites of illegal armed groups that had fired on the Syrian government army," the defence ministry said in a statement on Sunday evening.

The strikes destroyed underground shelters and training camps for the "Jabhat al-Nusra terrorist group", killing 34 fighters and injuring more than 60, it said.

Moscow used the old name for the group, which is currently known as the Hayat Tahrir al-Sham.

AFP was unable to verify the report.

The Syrian Observatory for Human Rights (SOHR) reported Russian strikes on the same day against the group, an Al-Qaeda spin-off, that killed five fighters.

The northwestern region of Idlib is the last remaining area of Syria under rebel control.

The Syrian government and Russian forces intensified strikes on sites in the region after a drone attack on a military academy in Homs last month killed more than 100 people, according to SOHR.

Russia and Turkey negotiated a ceasefire in Idlib in 2020 after an offensive by the Syrian government, but violations are frequent.