Terror attacks in Mumbai: Extremists 'copied al Qaida blueprint'
George Kassimeris, an expert in conflict and terrorism, said attacks on transport links, hotels and bars in Mumbai were "original" and "absolutely shocking".
He said the Islamic extremist group created the "modus operandi" of attacking vulnerable civilian targets with no warning, long-term plans or demands.
Witness accounts that gunmen were looking for US and British nationals suggest they want to grab international attention, he added.
Dr Kassimeris said: "Al Qaida set the blueprint for terrorist operations and now we see different people, different groups in different parts of the world, copying it.
"The underlying theme is to cause as much havoc as possible and this is exactly what has happened in India.
"There is no specific operational or logistical plan, they just want to inflict as much damage and injury as possible.
"The fact they have gone for western targets confirms initial fears these people are out to inflict as much damage as possible."
India has endured a series of terrorist attacks in recent years undertaken by disparate Islamic militants, many based in Pakistan and Bangladesh.
A relatively new extremist group known as Indian Mujahideen has claimed responsibility for several bomb attacks in Mumbai in the past 12 months.
Dr Kassimeris, a senior research fellow at the University of Wolverhampton, said those responsible were likely to be Islamic religious extremists.
He said: "It could be any one of them and it would be foolish to speculate so soon, but I am 99.9% sure there is a religious element to this."
A message explaining the attacks will probably be published via email or on an extremist website in the near future, the academic said.
He said: "Do not forget the fact that they are attacking high-profile targets means they will get high-profile publicity.
"This is the underlying reason they went for this kind of targets instead of just setting off a bomb in a far-flung suburb of Mumbai.
Dr Kassimeris said the terrorists might have chosen to use guns and grenades because some bomb plots have failed.
He said: "You need expertise to put bombs together. These people went for the straightforward style of terrorist activity. It is very easy and it works – unfortunately."
Another expert compared the attacks to the deadly bombing of the Marriott Hotel in Pakistan's capital Islamabad on September 20.
Professor Richard Bonney, the author of Jihad: From Qu'ran To Bin Laden, said the difference was that in Mumbai there were co-ordinated attacks and Westerners were singled out as hostages.
He said: "This attack looks more dangerous and better planned, though not directed against possible government targets but economic ones and of course the 'Western allies'."
The terrorists are believed to have entered Mumbai by sea, risk forecasters Exclusive Analysis said.
But the company's experts said they were "resistant" to reports that the attacks bore the hallmark of al Qaida or were even inspired by the jihadist movement founded by Osama bin Laden.
Indian intelligence has suggested the attackers may have been Pakistani, based on "loose evidence" that some of them spoke with a Pakistani accent, they said.
Exclusive Analysis said in its latest briefing: "The terrorists, who called themselves the Deccan Mujahideen – a previously unknown group – are believed to have used the sea route to enter the city with explosives.
"A boat filled with explosives and ammunition has been found near the Gateway of India and is said to have been safely defused.
"This exposes a security gap in Mumbai's defence because while the roads leading into and out of the city – and the state – are regularly patrolled and guarded with checkposts, coastal security appears to be a major security loophole."
"Deccan" refers to the Deccan plateau, which spreads across central and southern India, the company said.
It is unclear whether the name "Deccan Mujahideen" means the terrorists are from south India.
So far homegrown terror networks have mostly recruited members from northern and western India, Exclusive Analysis said.
The company's experts noted that it was "highly unlikely" the attacks on Mumbai was authorised or even known about at the top level in Pakistan.