Jihadists of the Islamic State group killed at least 50 Syrian soldiers in an ambush on Friday, summarily executing most of them after their capture, a monitoring group said.
The assault in Raqa province, the jihadists' Euphrates valley stronghold, came amid their fiercest assault yet on Damascus-held territory.
The deaths added to 74 already killed killed in the offensive across the north and northeast, the Syrian Observatory for Human Rights said.