MAZAR-I-SHARIF - The Taliban have killed 13 pro-government fighters in northern Afghanistan, ambushing them as they were on their way to take part in an operation against the insurgency, officials said Sunday.

The attack on the fighters, part of a local militia working with the government, took place Saturday afternoon in the volatile Chimtal district of northern Balkh province, some 40 kilometres from the provincial capital Mazar-i-Sharif.

It underscored rising insecurity in the war-torn country as the resurgent Taliban step up their assaults, with government forces struggling to contain them.

"13 local militia forces have been shot dead by Taliban insurgents as they were heading for an operation against the militants in Chimtal," Munir Farhad, spokesman for the provincial governor of Balkh told AFP.

"All of them were killed ... They were young forces," Farhad said, adding they were investigating the cause of the attack.

Sarwar Hussaini, police spokesman for northern Afghanistan confirmed the ambush and the death toll.

The Taliban, who have intensified their attacks on pro-government forces since launching their annual so-called "spring offensive", claimed responsibility for Saturday's attack.