Police in Peshawar, Pakistan continued their investigation on Saturday to try to identify a suicide bomber who killed at least 50 people during a holiday prayer service.

The blast on Friday happened at a crowded mosque in the northwestern part of the country.

Security officers arrested seven students from an Islamic school hours after the blast, which apparently targeted Pakistan's former interior minister, Aftab Khan Sherpao.

The bomber struck a mosque inside the politician's residential compound during prayers for the Islamic holy day of Eid al-Adha.

Sherpao escaped harm, but one of his sons was wounded and at least 50 people were killed.

The former minister survived an earlier suicide attack at a rally in a nearby town eight months ago that killed 28 people. 

The latest attack deepened the sense of uncertainty in Pakistan ahead of Jan. 8 parliamentary elections in which Sherpao is a candidate.

Police collected pieces of clothing, shoes, prayer mats and body parts from the scene of Friday's bombing, and investigators were examining them for clues to identify the bomber, an official involved in the probe said.
 
"We are looking at how it happened and who did it," said the official, speaking on condition of anonymity because he was not authorized to talk to the media.

Pakistani President Pervez Musharraf condemned the blast and directed security and intelligence agencies to track down those responsible, the state-run Associated Press of Pakistan reported.

UN Secretary General Ban Ki-moon also condemned the attack.
 
The bomber was in a row of worshippers when he detonated the explosive, provincial police chief Sharif Virk said Friday.