A Syria war monitor said that the death toll from a major rebel offensive on government-controlled areas in the country's north this week has risen to 412 people, including 61 civilians.

The toll in five days of clashes and air strikes "has reached 412", the Syrian Observatory for Human Rights said, including 214 rebels from Hayat Tahrir al-Sham and allied factions who launched the offensive, 137 pro-government forces and 61 civilians, 17 of them on Sunday.