QUETTA, Pakistan - At least 40 people were killed and dozens injured in a suspected bomb attack at a Shiite Muslim mosque in the southwestern Pakistani city of Quetta, sparking riots that forced the government to impose an indefinite curfew, officials said. Armed policemen and paramilitary troops spread out in the city, as local administration declared the curfew asking people to remain indoors, officials and witnesses said. "Curfew has been clamped down in Quetta and paramilitary and police have been deployed to control the rioting," said Brigadier Javed Cheema, head of the interior ministry's National Crises Management Cell. Asked if the security forces had been given orders to shoot rioters on sight, Cheema said it was "normal procedure in a curfew situation". The attackers hurled grenades and fired at the Friday congregation at the main Shiite mosque in Quetta, capital of southwestern Baluchistan province. Police said the exact number of assailants was still unclear, adding that one of them was blown up inside the mosque by a grenade and another was killed at the main entrance by mosque guards. A third suspected attacker wounded in firing died later in hospital, a police officer said. The attack was the second in less than a month against the Shiite ethnic Hazara community in Quetta. On June 8, 12 police trainees from the Hazara community were shot dead and another eight injured in Quetta. Photo by AFP/File/Banaras Khan