Updated

Syrian activists say a large explosion in a northern town along the border with Turkey has killed at least four people and wounded many others.

The Britain-based Syrian Observatory for Human Rights says the death toll in the town of Azaz is likely to climb after Wednesday's blast.

Both the Observatory and the activist-run Revolutionary Forces of Syria media office say the explosion is believed to have been caused by a car bomb. Images posted online by the activist-run Azaz Media Center showed a burnt out car and a fire in the area.