Who's Behind the Mumbai Massacre?

New York:Even as the siege of Mumbai was still going on, the finger-pointing began. India's Prime Minister Manmohan Singh said "external forces" were behind the attacks, a thinly veiled reference to India's neighbor and longtime foe Pakistan. Foreign Minister Pranab Mukherjee went further, telling reporters that "elements with links to Pakistan" were involved. But Pakistan's president and prime minister both condemned the attacks and rejected any talk of Pakistani involvement. Pakistani officials also announced that the head of the powerful Inter Services Intelligence organization — often accused of orchestrating terror attacks on India — would travel to India to offer assistance in investigating the Mumbai attacks.

There has been one claim of responsibility: a group calling itself the Deccan Mujahideen, which e-mailed news organizations on Thursday claiming it had carried out the attacks. The group, previously unknown, may be connected with (or even an alias of) the Indian Mujahedeen, which claimed responsibility for several terror strikes earlier this year. Indian terror experts say that both are likely to have connections to, or simply be renamed versions of, older Indian militant groups such as the Pakistan-based Lashkar-e-Toiba or the Students Islamic Movement of India. See pictures of two days of terror in Mumbai

Yet the scale and sophistication of the Mumbai attacks — which appear to have involved dozens of militants using assault rifles, grenades and explosives to simultaneously attack multiple targets — raise suspicions of involvement by more than one group, and if so, involving an unprecedented level of coordination.

"This is an operation of a very new type in India," writes Walid Phares on his well-respected counterterrorism blog "The 'emirs' have sent these armed elements in their 20s to strike at Indian psyche. One goal is to sink the Pakistani-Indian rapprochement� The goal is to target India as a power engaged in the war on terror but also to further destabilize the region, including Pakistan and its neighbor Afghanistan."

Here are the groups considered most likely culprits in the Mumbai attacks:

Lashkar-e-Toiba (Army of the Pure) formed in 1990, probably in Afghanistan. It is based near Lahore in Pakistan and is bent on forcing India out of Kashmir. It has also said it wants to restore Islamic rule over India. Indian intelligence sources believe the group has backers within Pakistan's ISI. It also has historic links to both the Taliban and al-Qaeda. India's National Security Adviser M.K. Narayanan said in 2006 that Lashkar-e-Toiba is part of the "al-Qaeda compact" and is "as big and as omnipotent" as Bin Laden's group.

 Jaish-e-Mohammed, which emerged in early 2000 under the leadership of Maulana Masood Azhar, who had been serving time in an Indian jail for Kashmir-related militancy but was released in exchange for Indian passengers on an Indian Airlines jet hijacked to Afghanistan. The group was responsible for an attack on India's parliament in December 2001, which brought India and Pakistan to the brink of war. Jaish-e-Mohammed is believed to have close links to al-Qaeda and Osama bin Laden through a religious school in Karachi.

The Students Islamic Movement of India, (SIMI) is last focused on Kashmir than either Lashkar-e-Toiba or Jaish-e-Mohammed. Indian authorities say the group, formed in 1977, has close connections to a pocket of Chicago's Muslim community. Its fortunes have waxed and waned over the past three decades, but the group has recently become more active again. SIMI blamed the 9/11 attacks on Israelis and, at the same time, expressed admiration for bin-Laden and his war against the West. Some Indian experts believe that Indian Mujahideen is simply a re-named SIMI.

In the past two years, the groups listed above have sometimes been joined in operations by the Bangladeshi arm of a group known as Harkat-ul-Jehadi Islami. The group is believed to be behind twin blasts in Hyderabad in 2007. Formed in 1992, in Dhaka, the Bangladeshi group has become a lot stronger in India since the massacre of Muslims by hardline Hindu nationalists in Gujarat in 2002.

Despite the ideological affinities of some of these groups with bin Laden's movement, Ajai Sahni, executive director of the New Delhi-based Institute for Conflict Management, says that there is no real evidence "of any operational linkages between al Qaeda and these groups." They may take inspiration from al-Qaeda propaganda, but they are unlikely to have direct organization links back to bin Laden.

More likely, however, is that the four separate groups have begun to work together more often, and in increasingly sophisticated ways. There have been instances in the past of the groups establishing joint operational cells. While pooling resources allowed for more effective operations, it also greatly increased the risks of police infiltration. As a result, the planning of such operations has been decentralized to the point that each group of militants attacking a specific target in Mumbai on Thursday were unlikely to have been aware of the total plan.

Sahni explains that previous experience suggests that an operation of the complexity of the Mumbai attacks would be directed by handlers based outside India, who design a plan and then contact militants within their networks based in India to carry out various missions — delivering explosives to a safe house, buying equipment, and so forth — that enable the gunmen to wreak havoc.

None of the India-based operatives would most likely know one another, and for the most part would not even meet. Contact with the handler is always through a public call center that makes it difficult to trace calls. If an operative is picked up by police, there is no way he can identify fellow plotters. "It assures total anonymity," Sahni told TIME last year. "The handler is in Bangladesh or Pakistan and the people here don't know each other. It's the most significant tactical shift in the near past and is a model for international terrorism in the future."

Sadly, the success of the Mumbai operation — at least 143 dead and, perhaps more importantly, two days of continuous news coverage and counting — is sure to embolden those behind it. The Indian model of disparate groups working together, if that's what it is in this case, is also likely to be copied by al-Qaeda-inspired terrorists around the world. The model, says Sahni, "is absolutely brilliant in every way."