Grenade-throwing Taliban militants dressed in military uniforms have stormed a court complex in northern Afghanistan, killing at least five people and wounding more than 30 others.

The ongoing assault in Mazar-i-Sharif city comes just before the start of the Taliban's traditional spring offensive.

That's set to be the first fighting season when Afghan security forces will battle insurgents without full NATO support.

Bodies of at least three dead policemen and 31 wounded people - some in a critical condition - have been taken to the provincial public hospital.