PESHAWAR, PAKISTAN // Investigators today searched a wrecked luxury hotel in northwestern Pakistan for evidence after a suicide bombing killed 17 people, including aid workers, in what the UN condemned as a "heinous terrorist attack". Elsewhere in the volatile region, security forces killed 70 suspected militants in an area close to two major Taliban tribal strongholds, intelligence officials said. No one immediately claimed responsibility for yesterday's attack on the Peshawar Pearl Continental, but the blast followed Taliban threats to carry out major attacks in large cities to avenge an army offensive against insurgents in the nearby Swat Valley. The Afghan president Hamid Karzai said in a statement: "Such barbaric attacks targeting civilians once again show that terrorism is a serious challenge facing all countries of the region. "Therefore the only effective tool to fight this menace is a serious and joint effort by all countries of the region in order to wage a real war against it." At least three suicide attackers shot their way past guards and set off the explosion late on Tuesday outside the hotel, a favourite spot for foreigners and well-off Pakistanis and a site that the US was considering for its consulate. The attack reduced a section of the hotel to concrete rubble and twisted steel and left a huge crater in a car park. Senior police official Safwat Ghayur said counterterrorism experts, police and intelligence agents were combing the rubble for clues on Wednesday. The Pearl Continental, affectionately called the "PC" by Pakistanis, is the most luxurious hotel in the rugged frontier city of 2.2 million. Relatively well-guarded and set back from the main road, it is near government buildings and overlooks a golf course and a historic fort. Security camera footage show the attackers in two vehicles, a white saloon and a small lorry. The vehicles pull up to a guard post outside the hotel, with the car in front. A puff of smoke then appears near the car window, and a guard standing at the post collapses, apparently shot. The vehicles then move into the hotel compound. A few seconds later, a flash and eruption of dust are visible, indicating a blast. Shafqatullah Malik, a senior police officer, estimated that the lorry was carrying more than half a ton of explosives. *AP/AFP