Pakistan-based terrorist outfit Lashkar-e-Tayiba had the backing of the Islamic nation's spy agency Inter Services Intelligence, which shared intelligence with Lashkar and provided protection to it in the Mumbai terror attacks, a media report said on Monday.
American intelligence and counterterrorism officials were quoted by the New York Times as saying that LeT has quietly gained strength in recent years with the assistance of Pakistan's ISI, which has allowed the group to train and raise money while other terrorists have been under siege.
Officials said though there is no hard evidence yet to link the spy agency to the Mumbai attacks, ISI shared intelligence with Lashkar and provided protection for it.
The ISI has shared intelligence with Lashkar and provided protection for it, the officials told the paper, and investigators are focusing on one Lashkar leader they believe is a main liaison with the spy service and a mastermind of the attacks.
"People are going back and looking at all the connections," one American counter-terrorism official, who was among several officials who spoke on condition of anonymity to the paper, was quoted as saying.
American and Indian officials believe that one senior Lashkar commander in particular, Zarrar Shah, is one of the group's primary liaisons to the ISI. "He's a central character in this plot," one American official said.
As a result of the assault on India's financial hub, American counterterrorism and military officials say they are reassessing their view of Lashkar and believe it to be more capable and a greater threat than they had previously recognised.
Pakistani officials have denied any government connection to the siege, in which nearly 200 people were killed in Mumbai.
One Pakistani official confirmed on Sunday that security forces have initiated an operation against at least one Lashkar camp in Pakistani territory.
The official, the Times said, gave no details about the operation, Pakistan's first known response against the group suspected of attacking Mumbai.
"The government of Pakistan has always said it would act on any evidence that is presented to us," the Pakistani government official told the Times. "We will make sure that nobody uses Pakistani territory to carry out terrorist activity."
While Al Qaeda has provided financial and other support to Lashkar in the past, the paper said, their links today remain murky.
Senior Qaeda figures have used Lashkar safe houses as hide-outs, but Lashkar has not merged its operations with Al Qaeda or adopted its brand, as did an Algerian terrorist group that changed its name to Al Qaeda in the Islamic Maghreb, American officials told the paper.
Unlike Osama bin Laden and his top lieutenants, who have been forced to retreat to mountain hide-outs in western Pakistan's tribal areas, Lashkar commanders have been able to operate more or less in the open, behind the public face of a popular charity, with the implicit support of official Pakistani patrons, the paper said, citing American officials.
For years, American intelligence analysts have described Lashkar as a group with deadly, yet limited, ambitions in South Asia. But terrorism experts said it clearly had been inspired by the success of Al Qaeda in rallying supporters for a global jihad.
"This is a group that years ago evolved from having a local and parochial agenda and bought into Al Qaeda's vision," Bruce Hoffman, a professor and terrorism expert at Georgetown University who has followed Lashkar closely for several years, told the paper.
As American, European and Middle Eastern governments crack down on Al Qaeda's finances, Lashkar still has a flourishing fund-raising organisation in South Asia and the Persian Gulf region, including Saudi Arabia, the Times quoted counterterrorism officials as saying. The group primarily uses its charity wing, Jamaat-ud-Dawa, to raise money, ostensibly for causes in Pakistan.
Lashkar, the Times noted, also has a history of using local extremist groups for knowledge and tactics in its operations. Investigators in Mumbai are following leads suggesting that Lashkar used the Students Islamic Movement of India, a fundamentalist group that advocates establishing an Islamic state in India, for early reconnaissance and logistical help.
Hoffman told the paper that Lashkar had developed particularly sophisticated Internet operations, and that intelligence officials believed the group had forged ties with regional terrorist organisations like Jemaah Islamiyah in Indonesia by assisting them with their own Internet strategies.
Pakistan is under intense international pressure, including from the US, to take action against the LeT for its involvement in the Mumbai attacks. The LeT was founded by militant ideologue Hafiz Mohammad Saeed, who formed the Jamaat soon after the Lashker was banned in 2001.