A suspected suicide attacker detonated a bomb at a Shi'ite mosque in the northwestern Pakistan city of Peshawar late Thursday, killing at least three people and wounded 20, police said. The blast comes as minority Shi'ite Muslims prepare to mark the Ashoura festival, which in previous years has been marred by sectarian violence involving rival Sunnis. Dawn TV cited witnesses saying six people were killed. It reported the Imambargah Qasim Baig mosque was crowded with worshippers at the time of the attack. Police official Abdullah Khan said the bomb went off as police stopped to search a man before entering the mosque.