Investigators said the bomber struck at a rally against a 2007 government raid of the capital city's Red Mosque, the Pakistan News Service PakTribune reported.

More than 40 people were injured in the blast with police officers representing most of the victims.

The PakTribune said police reservists appeared to have been the bomber's target and the final death toll was expected to increase as bomb officials search the area.

Nearly 100 people were killed July 10, 2007, when government forces raided the mosque on orders from President Pervez Musharraf. CNN said the raid occurred after radical students took control of the religious site, but several women and children were killed during the government action.

The raid prompted a spate of suicide attacks against both government and civilian targets, the news network said.