The Pakistani Taliban has said it was behind a suicide bomb that killed at least 53 Shi'ite Muslims at a rally in the country's southwest.The attack on the city of Quetta targeted Shi'ite Muslims who had gathered for Al Quds day. The annual event is held across the Islamic world to show unity with Palestinians living under Israeli rule. Following the attack, Shi'ite leader Allama Abbas Kumaili appealed for peace. "We understand these are attempts to bring Sunni and Shi'ite sects against each other," he said. Pakistan police said 53 people were known to have died in the bombing and 197 were in hospital for their injuries. Sky's foreign affairs editor Tim Marshall said it was the third major attack in Pakistan a week. On Wednesday, the Taliban claimed responsibility for a bombing which killed 33 people in the eastern city of Lahore."Of the 20% of Pakistanis who are Shia, they are under increasing attack from Sunni Islamic militanism," Marshall said. "They've taken this opportunity of a gathering to bomb them. "Why? In order to separate Pakistanis from each other, at the very time when the country is struggling because of the floods and make people fall upon each other so that the country falls apart." There were fears militant violence in Pakistan could escalate following the natural disaster that has left millions homeless. The US earlier said the devastating floods were likely to delay army offensives against Taliban insurgents. "Unfortunately the flooding in Pakistan is probably going to delay any operations by the Pakistani army in North Waziristan for some period of time," Defence Secretary Robert Gates said. Elsewhere in Pakistan a suspected US missile strike killed at least five militants. They were part of the Haqqani network which is working with the Taliban to fight Americans in neighbouring Afghanistan.