Syrian activists say the death toll from a government helicopter strike on a rebel-held town near the northern city of Aleppo has risen to 26 people, including four children.

The Britain-based Syrian Observatory for Human Rights says a military helicopter targeted a compound of the rebel group known as the Tawhid Brigade in the town of al-Bab. The bombs missed their target and hit the Nafasin market instead, killing 26 people, most of them civilians. Three of those who died in the attack were rebel fighters, said Rami Abdurrahman, who heads the Observatory.

The group initially reported six dead from the Saturday attack. It raised the death toll to 26 on Sunday when it received more information on the attack from activists on the ground.