At least 91 people have died in political violence sweeping Karachi, which has led to Pakistani troops being given the power to shoot-to-kill those involved in the unrest, according to officials. "The death toll in the violence has risen to 91," home ministry spokesman Sharafuddin Memon told AFP on Saturday. "More than 100 suspects, many of them with weapons, have been arrested," he said, noting that paramilitary troops were in control and patrolling streets in troubled parts of the southern port city, Pakistan's largest. Many people who were stranded due to unrest for four days were now going out safely, Memon said. Police and hospital officials confirmed the toll and arrests. The unrest has been blamed on loyalists of the Muttahida Qaumi Movement (MQM), the dominant local party that represents Pakistanis who migrated from India, and the Awami National Party (ANP) of Pashtuns from the northwest. In the worst incident, gunmen opened fire on two buses on Thursday, killing 12 people, including a six-year-old girl overnight, a security official said. The latest bout of violence comes just days after the MQM walked out of the federal government led by the Pakistan People's Party (PPP), a move which some analysts said made it harder for the government to intervene. The worst affected areas are impoverished, heavily populated neighbourhoods in western Karachi, dotted with construction sites where armed men of different ethnicities have exchanged gunfire.