By Michelle Nichols
NEW YORK (Reuters) - A car bomb defused in New York's Times Square was a potential terrorist attack, U.S. Homeland Security Secretary Janet Napolitano said on Sunday, but officials held off identifying who may be responsible.
The Taliban in Pakistan said it planted the crude device made of propane, gasoline and fireworks to avenge the killing in April of al Qaeda's two top leaders in Iraq as well as U.S. interference in Muslim countries.
The claim could not be immediately verified but security analysts urged caution, saying there could be links to Islamist groups or to a domestic cause in the United States.
"Either way we should know more soon," said Paul Rogers, a terrorism expert at Britain's Bradford University. "Because the explosives didn't go off, the forensics experts have a large amount of material in the vehicle to work on."
Senior FBI and police officials were due to hold a briefing at 3 p.m. EST (8 p.m. BST) on Sunday.
The Obama administration is "considering all possibilities, including that a terrorist group might have had a role," White House spokesman Robert Gibbs said.
Police, tipped off by a street vendor, found the bomb in a sport utility vehicle in Times Square when the entertainment and shopping area of Midtown Manhattan was packed with tourists and theatre-goers on a warm Saturday evening.
"We're taking this very seriously," Napolitano told CNN's "State of the Union" program. "We're treating it as if it could be a potential terrorist attack."
Police are examining security camera footage for clues after the vehicle was recorded travelling in the area but they have said no motive or suspect has been identified.
"The odds are quite high that this was a lone wolf," Senator Chuck Schumer told CNN, speculating that the suspect could be sympathetic to an Islamist or domestic group.
New York and its 8 million people have been on high alert since the September 11 attacks in 2001 when airliners hijacked by al Qaeda militants toppled the World Trade Centre's twin towers, killing more than 2,600 people.
Last year, police said they thwarted a plot to bomb the New York subway system. Two men have pleaded guilty in that case.
EARLY DAYS
Times Square was evacuated on Saturday evening but largely reopened early on Sunday with a heavy police presence. Broadway officials said all shows did go on, some beginning late.
"A few years ago I used to be nervous. Now it doesn't faze me," said Amy Grossman, a New York teacher waiting in line for theatre tickets on Sunday morning.
Similarities between the attempted attack in Times Square and another in London in 2007 included a vehicle abandoned in a crowded area with the intent of causing mass casualties, said Sajjan Gohel, director for international security at the London-based research company Asia Pacific Foundation.
"Was this done by an established group or, as in the London case, by self-radicalized people?" Gohel said.
Security camera footage could be the key for investigators, Gohel said, and voiced scepticism about the Taliban claim.
"The only way I can see this possibly having a genuine link to the Pakistani Taliban would be a home-grown bomber responding to inspiration from the group in some way," Gohel said.
Napolitano told ABC News there was no evidence the incident in Times Square was "anything other than a one-off" and that the bomb "doesn't look like it is a very sophisticated one."
"It lends itself to the idea that this was a low capability group or even a lone individual," said Henry Wilkinson, senior intelligence analyst at London-based security company Janusian, noting improvised bombs go wrong even for established groups.
"It's worth recalling the trend in radicalization in the U.S.A.," he added. "It does not look like a prototypical al Qaeda attack. But again it's early days."
The deadliest home-grown attack in the United States killed 168 people in 1995 when a truck bomb planted by Timothy McVeigh and another right-wing extremist exploded at a federal building in Oklahoma City.
NO IDEA WHO OR WHY
"We have no idea who did this or why," New York Mayor Michael Bloomberg told an early morning news conference.
Bloomberg said a T-shirt vendor noticed "an unoccupied suspicious vehicle" and alerted a police officer on horseback, who saw the dark-green Nissan Pathfinder had smoke coming from vents near the back seat and smelled of gun powder.
The bomb was found at about 6:30 p.m. (11:30 p.m. BST) on Saturday in the vehicle parked on 45th Street and Broadway with its engine running and hazard lights flashing. It had Connecticut licence plates that were from another vehicle.
The bomb squad removed and dismantled three propane tanks, consumer grade fireworks, two filled five-gallon (19-litre) gasoline containers, two clocks, batteries in each of the clocks, electrical wire and other components.
A locked metal box resembling a gun locker was also removed and taken to a safe location to be detonated.
"This wasn't make believe. This wasn't a false alarm," said Fire Commissioner Sal Cassano. "This was the real deal -- to hurt people."
New York police said they had searched transit hubs, landmarks and other sensitive areas after the Times Square bomb was discovered but did not find anything suspicious.
(Additional reporting by Steve Eder, Clare Baldwin, Jonathan Spicer and Deepa Seetharaman in New York, Jeremy Pelofsky and Ross Colvin in Washington and William Maclean in London; Editing by Howard Goller and John O'Callaghan)
