Fears are growing over the fate of hundreds of children believed to be held by jihadist extremists inside a besieged prison in north-east Syria.

Nearly 850 children are inside Ghwayran prison in Hasakah, which was stormed by Islamic State (IS) group fighters on Thursday, triggering days of battles.

At least 136 people have been killed since the jihadists launched their assault to try to free jailed fighters.

Thousands of IS suspects are held in prisons run by Kurdish authorities.