A suicide bomber disguised as a security officer struck the lobby of the U.N. food agency's Pakistan headquarters Monday, killing five people a day after the new leader of the Pakistani Taliban vowed fresh assaults, AP reported. The blast raises questions as to how the bomber managed to evade tight security at the heavily fortified World Food Program compound in the capital, Islamabad. It could also hamper the work of WFP and other aid agencies assisting Pakistanis displaced by army offensives against al-Qaida and the Taliban in their strongholds close to the Afghan border. Hours after the attack, the world body said it was closing its offices in Pakistan temporarily. «This is a heinous crime committed against those who have been working tirelessly to assist the poor and vulnerable on the front lines of hunger and other human suffering in Pakistan,» U.N. Secretary-General Ban Ki-moon told reporters in Geneva. Ban said the U.N. would continue providing humanitarian assistance to the Pakistani people. WFP spokesman Amjad Jamal said the food agency would not halt its aid to refugees fleeing fighting between militants and the army even while its offices were shut. -- SPA