Activists say the Syrian air force has carried out a chlorine gas attack on a northern town, killing six people.

A military official immediately denied the claims and blamed the rebels fighting to topple President Bashar Assad.

The Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees said on Tuesday that the attack targeted the town of Samrin the previous night. The two activist groups say it also injured dozens.

An opposition official in the area says there were two attacks, the first targeting rebels while the second hit a residential area. He says the six killed were members of the same family, including three children.

The officials spoke on condition of anonymity because they were not authorized to talk to reporters.