According to the sources, the policemen were on their duties at railway track of Link Baduni Road when some unknown assailants opened fire on them and all the four personnel died on the spot.

The bodies were shifted to the nearby hospital.

Later, the police cordoned off the area and began snap checking and set up blockades all over the city.

Pakistan sits on the frontline of the US-led war on Al-Qaeda and since July 2007 has been gripped by a local Taliban-led insurgency, concentrated largely in the northwest.

In the last five years, attacks blamed on Islamist bombers have killed more than 5,000 people, according to an AFP tally.