Pakistan's Taliban chief has claimed responsibility for a deadly assault on a police academy, saying he wanted to retaliate for US missile attacks on the militant bases on the border with Afghanistan.

Baitullah Mehsud, who has a $5 million bounty on his head from the United States, also vowed to "amaze everyone in the world" with an attack on Washington or even the White House.

The FBI, however, said he had made similar threats previously and there was no indication of anything imminent.

Mehsud, who gave a flurry of media interviews Tuesday, has no record of actually striking targets abroad although he is suspected of being behind a 10-man cell arrested in Barcelona in January 2008 for plotting suicide attacks in Spain.

Pakistan's former government and the CIA consider him the prime suspect behind the December 2007 killing of former Prime Minister Benazir Bhutto. And Pakistani officials accuse him of harboring foreign fighters, including Central Asians linked to al-Qaida, and of training suicide bombers.

But analysts doubt that Taliban fighters carried off Monday's raid on the Lahore academy on their own, saying the group is likely working more closely than ever with militants based far from the Afghan frontier.

It's a constellation that includes al-Qaida, presenting a formidable challenge to the US as it increases its troop presence in the region, not to mention nuclear-armed Pakistan's own stability.

Mehsud said the academy and other recent attacks were revenge for stepped-up American missile strikes into Pakistan's border badlands.

"Soon we will launch an attack in Washington that will amaze everyone in the world," Mehsud said in a telephone interview. He offered few details, though in a separate recorded conversation with local Dewa radio station, he said the White House was a target.

FBI spokesman Richard Kolko said the bureau was not aware of any imminent or specific threat to the US, despite what the Pakistani Taliban leader said.

"He has made similar threats to the US in the past," said Kolko.

State Department spokesman Gordon Duguid said he had not seen any reports of Mehsud's comments but he would "take the threat under consideration."

The ruthless attack on Lahore's outskirts Monday left at least 12 people dead, including seven police, and sparked an eight-hour standoff with security forces that ended when black-clad commandos stormed the compound. Some of the gunmen blew themselves up.

The siege-style approach using heavily armed militants came just weeks after the deadly ambush of Sri Lanka's visiting cricket team in the heart of Lahore. Both attacks were reminiscent of November's siege of Mumbai, India - also blamed on Pakistani militants.

A senior police investigator, Zulfikar Hameed, told Dawn News TV the men arrested for the attack have corroborated Mehsud's involvement.

Besides Mehsud, a little-known group believed linked to him also claimed credit. Mehsud declined to discuss the group, Fedayeen al-Islam, or any others who might have been involved.

Pakistan Interior Ministry chief Rehman Malik said one captured attacker was Afghan and the initial investigation suggested the conspiracy originated in South Waziristan tribal region, Mehsud's stronghold. But Malik also said the al-Qaida-linked group Lashkar-e-Jhangvi might have played a role. Officials have said three gunmen are in custody.

"In my view, it's not done by one group," said Mohammed Amir Rana, a Pakistani analyst well-versed in the intricacies of militant groups. "One group has the major role in providing the fighters or one group might be providing the logistics or intelligence. And one group provided the financing."

A variety of militant groups operate in Pakistan beyond al-Qaida and the Taliban, and officials and analysts say it appears the coordination among some of them is increasing. Of particular concern are violent groups based in Punjab, Pakistan's most populated province, which borders India.

Some Punjabi groups have their roots in the dispute with India over the Kashmir region. The Pakistani spy agency is believed to have helped set them up and maintain some links, a prospect that vexes US officials.

Others have different origins.

Jhangvi, for instance, is a sectarian extremist group blamed for a stream of atrocities against minority Shiite Muslims. In recent years, it has evolved, Rana said, and is believed to provide foot-soldiers and suicide bombers for al-Qaida operations.

The groups' membership is fluid and overlapping. They are riven with feuds. But analysts say they are finding a common cause in striking America and its allies, while also focusing on spreading Taliban-style rule over more and more of Pakistan.

Interviews in recent months with three Afghan and Pakistani Taliban operatives, who demanded anonymity for security reasons, suggest a Pakistani crackdown on some groups following the Mumbai assault has prompted many operatives of Punjab-based groups to seek sanctuary in the northwest.

The Mumbai attacks were specifically blamed on Lashkar-e-Taiba, a Punjab-based group fighting in Kashmir.

The militant activity may also relate to American plans to send thousands more troops to Afghanistan, where the Taliban have roared back more than seven years after the US-led invasion ousted their regime, said Shaun Gregory, an analyst at Britain's University of Bradford.

With more allies, the Taliban may feel more capable of taking on grander assaults like that in Lahore as opposed to suicide bombings favored when their resources are more depleted, he said.

Mahmood Shah, a retired military officer, voiced concern that the Taliban were embarking on a campaign of terror in Punjab similar to that employed in the northwest, where hundreds of police were killed before militants turned their attention to political leaders.

While the pro-West ruling party has been trying to persuade a skeptical public to close ranks against an increasingly powerful nexus of militant groups, it has been largely preoccupied with squabbles over power and privileges with a key opposition party.

Adm. Michael Mullen, chairman of the US Joint Chiefs of Staff, said Tuesday he believes the Pakistani government is focused on the rising threat of extremist violence.

"They are responding and that's a tide that must be stemmed," he told reporters in Washington.

But doubts remain about whether the powerful Pakistani military is committed to sidelining extremist groups it has used as proxies against India and Afghanistan.

Defense analyst Ayesha Siddiqa said Pakistan must evaluate its own links to some of these groups if it is to survive.

"We have to dig this out of our past," she said. "Unless we do that, unless we have a consensus on our strategy ... we aren't going to go anywhere."

(Chinadaily.com.cn via agencies April 2, 2009)