ISLAMABAD — A suicide bomber who killed five staffers at the U.N. food agency's headquarters in Pakistan was dressed as a security officer and allowed to enter the heavily guarded building after he asked to use the bathroom.
The United Nations announced it was temporarily closing all its offices in Pakistan after the midday Monday bombing, which blew out windows and left victims lying in pools of blood in the lobby of the three-story World Food Program compound.
"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 said in Geneva.
Despite the office closures, the U.N. said its Pakistani partner organizations would continue distributing food, medicine and other humanitarian assistance. The world body said it would reassess the situation over the next several days.
Pakistani authorities launched an investigation into the major security lapse, saying they would question guards who failed to stop the bomber from carrying out the first suicide attack in Islamabad in four months.
Taliban leader vows attacks
The attack came a day after the new Pakistani Taliban leader met reporters close to the Afghan border, vowing more attacks in response to U.S. missile strikes on militant targets in Pakistan. Ending speculation he had been killed, Hakimullah Mehsud denied government claims the militants were in disarray and said his fighters would repel any army offensive on their stronghold in South Waziristan.
Authorities blamed Islamic militants for Monday's bombing but did not single out the Taliban.
It was unclear whether militants targeted the World Food Program because of its work in Pakistan or were simply looking to kill foreigners or those working with them. The dead were four Pakistanis and an Iraqi.
Extremists in Pakistan, Afghanistan and Iraq seeking to attack high-profile Western targets have shown no hesitation in striking foreign humanitarian agencies, including the United Nations, regardless of the work they are doing in relieving the suffering in the countries. A blast in June on a luxury hotel housing many foreign aid workers in the northwestern city of Peshawar killed two U.N. staffers and wounded others.
Video: Chaos on streets after blast Sometimes the very nature of their work invites attack. In Monday's bombing, insurgents may have believed that by feeding refugees from the fighting in the Swat valley, the World Food Program is propping up a Pakistani government they view as a U.S. puppet or somehow supporting the army offensive there.
The U.N. and various humanitarian agencies, including those funded by the U.S. government, have been expanding in Pakistan over the last year to help support its elected government.
12-foot-high blast walls
The United Nations considers itself a major target in Pakistan. Many of its offices are surrounded by 12-foot-high blast walls. Its staff members are driven in bulletproof cars and not allowed to bring their families with them on assignment in the country.
The World Food Program compound, which employs more than 70 people, is surrounded by square metal cages filled with sand and small stones used to protect against blasts and projectiles.
Asked whether security had been bolstered following last month's attack that killed 12 African U.N. peacekeepers in a U.N.-authorized mission in Somalia, Montas replied: "Not that I know of."
Taliban and allied militants have carried out scores of suicide attacks in Pakistan over the last 2 1/2 years. Under U.S. pressure, Pakistani security forces have recently had some success combatting the extremists. Hakimullah's predecessor, Baitullah Mehsud, was killed in a U.S. drone strike in August.
Four big strikes in three weeks
Monday's bombing was one of at least four major strikes in the past three weeks that would appear to show Pakistani militants are regrouping and have retained the capacity to carry out attacks. It took place in a well guarded, upscale residential area close to where President Asif Ali Zardari has a home.
Hassan Abbas, a former official in the Bhutto and Musharraf governments, said the attack is significant because it shows militants can still breach high security zones. "Probably, terrorists were able to penetrate the local security infrastructure," Abbas said.
Police official Bin Yamin said the bomber detonated his explosives in the lobby. Typically, visitors to U.N. buildings in Islamabad are screened and patted down for weapons and explosives in secure chambers some distance from the entrance to the building. It was unclear whether the attacker went through that process.
Security camera footage broadcast on local TV shows the bomber walking through a door into what appears to be the main building carrying a 2-foot-long cylindrical object — possibly a detonator — in one hand. Seconds later, a bright flash fills the screen.
"There was a huge bang, and something hit me. I fell on the floor bleeding," said Adam Motiwala, an information officer who was hospitalized with wounds to his head, leg and ribs.
Medical officials at two hospitals said five staff members were killed, including two Pakistani women, two Pakistani men and an Iraqi. Several others were wounded, two of them critically, the WFP said in a statement.
Interior Minister Rehman Malik said the attacker was wearing the uniform of the paramilitary police unit guarding the outer perimeter of compound. He said the bomber, who was in his 20s, asked if he could go inside the building to use the bathroom. He was carrying around 18 pounds of explosives.
"We are investigating those security officials who were present and on the duty and who allowed him inside," he said.
Malik said the bombing proved the militants were growing desperate in response to recent government offensives against the groups. Polls have shown that the Pakistani public has been losing patience with the militants this year.
"These terrorists," Malik said, "they are injured snakes."
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