Sararogha, Pakistan ? Flanked by heavily armed fighters, the new leader of the Pakistani Taliban sat on a blue blanket, amiable and relaxed as he cracked jokes and mixed in threats of vengeance for deadly U.S. airstrikes.

One day later, a suicide bomber attacked a U.N. office in Islamabad.

Hakimullah Mehsud met with reporters Sunday for the first time since winning control of the militant group, quashing speculation that he had been slain in a succession struggle following the killing of his predecessor in a U.S. drone attack.

He also described his group’s relationship to al-Qaida as one of “love and affection.” Osama bin Laden and other top al-Qaida leaders are believed to be hiding out in the remote border region with Afghanistan, possibly in territory controlled by Hakimullah.

The militant vowed to retaliate against the U.S. and Pakistan for deadly attacks on his allies and said his fighters will repel an anticipated Pakistani offensive into his stronghold.

Hakimullah made his threat of vengeance hours before a suicide bomber disguised as a security officer killed five people at a U.N. office in Islamabad on Monday. There was no immediate claim of responsibility, but authorities blamed Islamic militants.

Pakistani Interior Minister Rehman Malik has said several times that officials believed Hakimullah — and possibly his deputy, Waliur Rehman — had been killed in fighting over who would replace Baitullah Mehsud after his Aug. 5 death in a missile strike. Malik said that Hakimullah was being impersonated by his brother, including in calls to media organizations.

Western diplomats in Islamabad had also said their intelligence indicated he may have been killed, while Western media reports over the weekend quoted American officials as saying they believed he may be dead.

Hakimullah was very much alive, speaking calmly as he sat under a tree on a blanket surrounded by top Taliban commanders, including Waliur Rehman, in a show of unity in South Waziristan, where the Pakistani state and security forces have little or no presence. Also present were Qari Hussain, the head of the Taliban’s suicide bomb faction, and Azam Tariq, a Taliban spokesman.

He told five Pakistani reporters, including one from The Associated Press, that the group’s leadership remained intact and unified.

“We all are sitting before you, which proves all the news about myself … was totally baseless and false,” he said.

Pakistani security authorities were not immediately available for comment.

Pakistan has largely beaten back a Taliban insurgency in the northwestern Swat Valley in recent months and intelligence officials say the country is preparing a major offensive against al-Qaida and the Taliban in South Waziristan. The military has been blockading the region and seeking to encourage other tribes to rise up against Hakimullah.

Hakimullah said his forces were ready for such an attack, which would likely be far tougher than the Swat campaign. The army has been beaten back there three times since 2004. Analysts say some 10,000 well-armed militants, including foreign fighters, are in the mountainous region and well dug in.

“We are fully prepared for that operation and we will give full proof of those preparations once the offensive is launched,” he said.