ISLAMABAD: Pakistan blamed Taliban militants Tuesday for the deadly suicide bombing at the UN food agency's heavily fortified compound in the capital as authorities detained some of the guards posted outside to try to determine how the attacker gained entry.

Police and security forces survey UN World Food Programme (WFP) offices in Islamabad after a suicide bomb attack October 5, 2009. [Agencies]

The suicide bomber, who killed five people at the World Food Program's Pakistan headquarters Monday afternoon, was dressed as a security officer and was allowed to enter - apparently bypassing the normal security procedures - after asking the guards outside if he could used the bathroom.

"We should expect a few more (attacks)," he said.

After the attack, the UN announced it was temporarily closing all its offices in Pakistan, but 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.

Malik, who was visiting those injured in the bombing at a Pakistani hospital, said the government had taken several of the guards outside the UN offices into custody for questioning as part of the investigation into the security lapse.

"All the security arrangements were in place at the UN office," he said.