A bomb blast in the central Pakistani city of Multan injured three policemen on Sunday, a police official said, correcting his earlier report that the three had been killed. \"The bomb explosion targeting a police checkpost wounded three police officers,\" Multan city police chief Aamir Zulfiqar said. \"It seems that the bomb was planted on a motorbike parked close to the police post,\" he added. Prime Minister Yusuf Raza Gilani condemned the attack, an official statement said. Nearly 4,500 people have been killed across Pakistan in attacks blamed on Taliban and other Islamist extremist networks based in the tribal belt since government troops stormed a radical mosque in Islamabad in 2007. Militants have stepped up their activities, mostly targeting security forces, to avenge the death of Osama bin Laden who was killed in a covert operation by US Navy SEALs in the Pakistani garrison city of Abbottabad in May.