DUBAI (Reuters) - The Pakistani Taliban claimed responsibility for the attempted car bomb attack in New York’s Times Square, a statement on an Islamist website said on Sunday.

It was not immediately possible to verify the authenticity of the claim. Security officials have urged caution, saying there could be links to other Islamist groups or to a domestic cause in the United States.

“The Pakistani Taliban announces its responsibility for the New York attack in revenge for the two leaders al-Baghdadi and al-Muhajir and Muslim martyrs,” said a statement on a website commonly used by Islamists.

Al Qaeda’s Iraq leader Abu Ayyub al-Masri -- also known as Abu Hamza al-Muhajir -- and Abu Omar al-Baghdadi, the purported head of its local affiliate, the Islamic State of Iraq, were killed last month.

U.S. Homeland Security Secretary Janet Napolitano said on Sunday that the car bomb defused in New York’s Times Square may have been a terrorist attack. Officials held off identifying who might be responsible for the crude device, made of propane, gasoline, and fireworks.

Police found the car bomb, which was defused on Saturday evening, in a sport utility vehicle when the area was packed with tourists and theater-goers.

The al Qaeda-backed Pakistani Taliban is waging a bloody campaign marked by repeated suicide attacks to topple the U.S.-supported Pakistani government.

The Afghan Taliban shares the group’s anti-Western views and its ethnic Pashtun identity but has refrained from attacking the Pakistani government.

The Pakistani Taliban suffered a series of setbacks over the past year during Pakistani army offensives in their strongholds, including South Waziristan, which killed hundreds of militants and destroyed their bases.

But the group surprised observers with its apparent involvement a suicide bomb attack near Khost in eastern Afghanistan on December 30. that killed seven CIA employees in the second worst attack in the spy agency’s history.

Its leader Hakimullah Mehsud appeared in a video showing him sitting beside a Jordanian militant who crossed over Pakistan’s border and carried out the attack.

The Islamist website (here) said that Qari Hussain Mehsud, known as the master mentor of Taliban suicide bombers, accepted responsibility for the failed New York attack "with great pride and utmost bravery."

Mehsud, a cousin of Hakimullah Mehsud, is considered one of the most powerful Taliban leaders.

A video made by “Taliban News” on YouTube had a prepared video with English subtitles claiming responsibility for the attempted New York attack, but the video was quickly taken down and is now unavailable.

Hakimullah Mehsud was widely believed to have been killed by a U.S. missile strike in South Waziristan in January but on April 29, Pakistani intelligence officials said they believed he was alive, contradicting earlier comments.

Washington, while cautious about making pronouncements about Mehsud’s fate, said it was clear he was no longer “operational” or in charge of the group. If it is confirmed Mehsud is alive, it would be a blow for the CIA, which had intensified drone attacks after Mehsud appeared in the video with the Jordanian.