Weeks after carrying out a bloody suicide bombing in the heart of Pakistan's capital, suspected militants struck again on a high security police complex in Islamabad and also hit a jail van in NWFP, killing 16 and injuring ten.

The casualties were less in the police lines complex attack in Islamabad as the suicide bomber struck the Anti-Terrorism Squad office when most of the security personnel were out on patrol in view of the joint session of the Parliament reviewing strategy to combat upsurge in violence.

Though initial reports had put the casualty figure at eight killed, the Islamabad Chief Commissioner Kamran Lashari later said ten people were injured.

Confusion prevailed as officials did not know the whereabouts of a police commando team which had left the building minutes before the blast. But, police officials said the casualty figure was clarified when the team returned.

There was also confusion over how the attack was carried out. Some reports said a suicide bomber rammed an explosive-laden vehicle into the building, while others said a man carrying boxes of sweets came out of the car and entered the ATS office shortly before the blast occurred.

Officials said they had found a letter in Pashto at the blast site warning more such attacks would be carried out if the Pakistan government does not stop supporting the war on terror.

The attack follows the deadly September 20 suicide blast on the five-star Marriott hotel in Islamabad that claimed nearly 60 lives. The Marriott was considered popular among foreigners.