All Syrian fighters of the Islamic State group have left the jihadists' one-time bastion of Raqa and preparations are under way for foreign combatants to leave, a monitor said Saturday.

The Syrian jihadists left Raqa with their families, heading to unknown destinations, the Britain-based Syrian Observatory for Human Rights said.

A Raqa official said Syrian IS members had surrendered to the US-backed Syrian Democratic Forces battling to take full control of the city, without specifying how many.