The Syrian Observatory for Human Rights (SOHR) said as many as 56 pro-Turkey fighters were killed when Russian warplanes attacked their training camp in northwestern Syria.
The organisation reported that Russian planes targeted a training camp controlled by the Faylaq Al-Sham faction in the Jabal Duwayli area in Idlib province, killing at least 56 fighters and wounding more than a hundred others.
SOHR Director Rami Abdel-Rahman told AFP that the Russian warplanes targeted the newly equipped training camp while dozens of fighters were inside.
Meanwhile, the media spokesman for the National Liberation Front (a coalition of Idlib-based opposition factions), Saif Al-Raad confirmed to AFP that Russia had targeted the faction's training camp, without specifying the final death toll.
Al-Raad condemned the "Russian warplanes and the regime forces' continued violation of the Turkish-Russian ceasefire agreement by targeting military sites, villages and towns."
In March, Turkey and Russia reached a ceasefire agreement which covered areas in and around Idlib. While the ceasefire is still in place, violations take place from time to time.