Russia blamed for airstrike on training camp in north-west Syria

Rebel groups vow to retaliate after attack in Idlib that reportedly killed 50 Turkish-backed fighters

An airstrike on a rebel training camp in north-west Syria killed more than 50 Turkish-backed fighters and wounded nearly as many, in one of the heaviest blows to the opposition's strongest groups, a spokesman and a war monitor said.

The opposition vowed to retaliate for the attack on Monday on Faylaq al-Sham, blaming Russia for the daytime attack. There was no immediate comment from Russia or Turkey, which have worked together to maintain a ceasefire in the rebel enclave, although they support opposite sides in Syria's conflict.