Air strikes by Russia killed 78 Turkey-backed rebels in northwestern Syria Monday, a monitor said, in the bloodiest surge in violence since a truce almost eight months ago.

More than 90 others were wounded when Russian warplanes targeted a training camp of the Faylaq al-Sham faction in the Jabal Duwayli area in Idlib province, the Syrian Observatory for Human Rights said, AFP reported. 

In early March, a truce brokered between Moscow and Ankara stemmed a deadly month-long Russia-backed regime military offensive on the country's last major rebel stronghold in Idlib.