(RFE/RL) -- A suicide bomber has blown himself up at the UN's World Food Program office in Islamabad, killing at least five people and wounding several others.
Details about the attack in Pakistan's capital are still emerging. Police said initial evidence suggests the bomber was a man in his 20s who got inside the lobby of the heavily guarded UN building by disguising himself as a security officer.
The attack has raised questions about the state of security at the UN compound. Typically, visitors to UN compounds in Islamabad are screened and searched for weapons and explosives in secure chambers before they get close to the entrance of a UN building.
The blast also could hamper the work of the World Food Program and other aide agencies that are trying to help poor and hungry Pakistanis.
About 70 people worked in the UN building as part of the effort to distribute food to impoverished Pakistanis -- including those in the northwest who have been displaced or affected by a Pakistani Army offensive this year against militants in the Swat Valley.
The British defense and home ministers were visiting Islamabad at the time of the attack but were unaffected.
Waseem Khwaja, a spokesman for the Pakistan Institute of Medical Sciences, said the slain victims include an Iraqi man who worked for the World Food Program and at least two Pakistani women.Taliban Leader Alive
There was no immediate claim of responsibility for the bombing. But attention has focused on Pakistani Taliban fighters in and around the Swat Valley whose new leader, Hakimullah Mehsud, has warned of a fresh wave of attacks against Pakistan and the United States.
Hakimullah Mehsud talks with reporters in November 2008.
Pakistani Interior Minister Rehman Malik said the attack was an act of desperation from a militant movement that has been virtually crushed by a Pakistani government offensive that began earlier this year:
"The operations that we had carried out against [the Taliban] in Swat, North Waziristan, and South Waziristan, have broken their back. They are like a wounded snake," Malik said.
"Five days earlier, they held a meeting in which they decided that they would target specific people to put pressure on the government and the Pakistani people."
On October 4, Hakimullah Mehsud met with reporters in Pakistan's rugged tribal agencies for the first time since taking over as the top Pakistani Taliban commander.
Flanked by other Taliban leaders in a show of support, he said his fighters would avenge the killing in August of the previous Pakistani Taliban leader, Baitullah Mehsud, by a U.S. drone missile strike.
Hakimullah Mehsud also complained about an increasing number of drone attacks in the tribal areas along the border with Afghanistan.
Pakistan's government publicly protests the U.S. drone attacks. But Islamabad is believed to sanction individual attacks and to have even provided intelligence for some strikes.
U.S. officials have said they are considering a strategy of intensified drone attacks combined with the deployment of special forces against Al-Qaeda and Taliban targets on Pakistan's side of the border with Afghanistan.
Analysts say the Pakistani Taliban is now struggling to regroup from a months-long offensive in and around the Swat Valley by Pakistan's army. The militant movement has also seen several of its leaders killed by drone missile strikes since last year. That is thought to have caused a power vacuum and struggle among Taliban leaders in Pakistan.
The appearance of Hakimullah Mehsud has ended speculation by Pakistani military officials that he had been killed in August during a power struggle within the militant movement after Baitullah Mehsud's death.Warning of Attacks
Pakistan's "Dawn" newspaper has warned of a growing threat of suicide attacks. It quoted unnamed Pakistani intelligence sources as saying that the Taliban has vowed to carry out large-scale suicide attacks across Pakistan to avenge Baitullah Mehsud's death.
A bloodied UN employee after the attack
The intelligence sources also described the Pakistani Taliban as "disturbed and frustrated" since the release of a video showing the dead body of Baitullah Mehsud.
Indeed, intelligence agencies have warned Pakistan's Interior Ministry about a rise in militant activities in different parts of the country in recent weeks. The government also has asked the authorities to increase security in the Northwest Frontier Province, as well as the Punjab, Baluchistan, and Sindh provinces.
Baitullah Mehsud was one of Pakistan's most wanted and dreaded terrorists. He had $5 million bounty on his head. Authorities in Islamabad also accused him of plotting the assassination of former Prime Minister Benazir Bhutto in December 2007.