ANALYSIS - Daring Mumbai attacks reveal any city's vulnerability

By Luke Baker

LONDON (Reuters) - Whatever group lies behind the attacks in Mumbai, security experts say one thing has been made abundantly clear: a massive city can be reduced to mayhem if a group of men is well-enough armed and prepared to die.

Rather than hijacking planes as in Sept. 11, or smuggling delicately wired car bombs into a city, the Mumbai gunmen chose a frontal style of armed assault, killing more than 100 people, wounding around 250 and causing immense panic in a thriving city of 13 million.

Security specialists say the attack was probably months in the planning and appears to have been finely tuned in its execution, but it ultimately relied on only an estimated 25 gunmen lightly armed with assault rifles and hand-grenades.

Their ability to roam around and sustain the attack, while all the while being willing to die in the onslaught, made it all the more difficult to combat and far more drawn out than an instantaneous suicide bomb attack might have been.

"It's virtually impossible to stop 20 guys with guns from attacking anywhere in the world if they are prepared to die," said Sajjan Gohel, an analyst with the Asia-Pacific Foundation, an independent security and intelligence group based in London.

"That is the thing about the fedayeen strategy," he said, using an Arabic term used to describe self-sacrificial gunmen who have operated in Iraq, Kashmir and across the Muslim world.

"It's even more effective than a suicide mission. With a suicide mission, you blow up your explosives and you're gone. With a fedayeen attack, you try to last out as long as possible, killing as many people as possible," he told Reuters.

Nearly 20 hours after the attack began late on Wednesday night, Indian soldiers and the militants were still exchanging gunfire and more than 100 people were trapped inside the Taj Mahal hotel, one of two five-star hotels popular with Western tourists and businessmen that were targetted in the assault.