PESHAWAR: Three policemen were killed when a group of heavily-armed Taliban militants attacked a checkpost in northwest Pakistan, a senior police official said.

The ambush happened on the outskirts of Peshawar, the capital of the North West Frontier Province (NWFP), swathes of which are plagued by a Taliban-led insurgency to enforce a harsh brand of Islamic law.

"A group of some 20 militants armed with rockets, hand grenades and assault rifles attacked Arbab Tapo checkpost. Three policemen were martyred in the attack," Abdul Ghafoor Afridi, senior Peshawar police official, told AFP.

The attackers escaped after a gun battle, he added.

Pakistan's military are fighting a nearly two-month-long campaign to dislodge Taliban rebels from three NWFP districts, and have said they will open up a second front in the lawless tribal areas along the Afghan border.

The semi-autonomous northwest tribal zones are a stronghold of Pakistan Taliban commander Baitullah Mehsud, who is blamed for a wave of deadly attacks in Pakistan over the past two years, many hitting Peshawar.