Five people have been killed after a suicide bomber attacked the UN World Food Programme offices in the Pakistani capital Islamabad.The bomber was dressed in combat fatigues and gained entry into the heavily fortified compound by asking a guard if he could use the toilet. The blast killed four Pakistani nationals and an Iraqi, two of the dead were women. The World Food Programme has been hard at work providing relief for two million people displaced by an army offensive against militants in the Swat valley. UN Secretary General Ban Ki Moon expressed his outrage. He said: “This is a heinous crime committed against those who have been working tirelessly to assist the poor and vulnerable on the front line of hunger and other human suffering in Pakistan.” No group has claimed responsibility for the carnage, but suspicion has fallen on the Pakistani Taliban which vowed revenge after their leader Baitullah Mehsud was killed by a US drone in August.