ISLAMABAD, Oct. 5 (Xinhua) -- Pakistani Interior Minister Rehman Malik said on Monday that the suicide bomber, who struck the UN's World Food Program (WFP) office in Islamabad, was wearing police uniform.

    The bomber exploded his bomb at the reception of the WFP office and killed an Iraqi employee and two Pakistani female employees, according to police at the scene.

    One more person died later in the hospital, raising death toll to four, the interior minister told reporters after visiting the WFP office. He said up to seven kilograms of explosives were used in the attack.

    Malik said that a guard at the WFP office gate allowed the bomber to enter after he requested to use toilet. "We are investigating as to why the guard allowed the bomber to enter the building," he said.

    The militants can use officials' cars for attacks and the same has been conveyed to the security agencies, he added.

    The minister blamed the militants for the attack and said that Pakistani Taliban had assigned suicide bombers and there may be more attacks in the coming days and weeks.

    "We have taken action against the militants in Swat and Waziristan and have broken their back. The militants had a meeting and decided to launch attacks on some personalities," he said.

    "We had issued security alert as the detained Taliban leaders have said they had deputed suicide bombers. They have a strategy and in coming weeks more incidents could happen," Malik said.

    He said a joint investigation team has been formed to investigate the suicide attack. The team includes experts from the intelligence agencies and police, he added.

    He said the government has asked the UN and other foreign missions to move to the highly guarded Diplomatic Enclave from the populated area.

    He said the militants are bent upon destabilizing and defaming Pakistan. "The UN had been involved to help the Internally Displaced Persons and had been distributing food from here, but the militants want to disrupt the process," he said.

    The blast happened at a time when the British Defense and Home secretaries and a top UN official visiting Pakistan.

    "The militants want to send message to the visiting dignitaries. But the nation says no to Taliban, no to terrorist," the interior minister said.

    He said Taliban militants have sent six messages to the government for reconciliation. "We have told them to lay down arms first," he said.

    He said the remnants of the militants will face action as the Pakistani security forces had in Swat valley and Bajaur and Mohmand tribal regions in the northwest.

Special Report: Pakistani Situation