Pakistan's military intelligence agency, the ISI, was heavily involved in 2008 Mumbai terrorist attacks, a 109-page classified Indian government report obtained by the British newspaper The Guardian alleges.

The report is based on confessions of American Lashkar-e-Tayyiba (LeT) operative David Headley who scouted targets for the attacks under instructions from the Pakistani terror group LeT. More than 160 people were killed in the Mumbai attacks, including six Americans.

Headley struck a plea bargain with U.S. authorities in March and confessed to all 12 terrorism charges brought against him, including conspiracy to bomb public places in India, to murder Americans and others in India, and to provide material support to the Lashkar-e-Tayyiba. In interviews with Indian investigators from the National Intelligence Agency (NIA), Headley detailed numerous meetings between Pakistani intelligence officers and Lashkar members. He claimed at least two of his reconnaissance missions to India to scout potential targets were paid in part by the ISI and he reported regularly to the spy agency.

According to Headley, the Mumbai attacks were in part a result of ISI efforts to boost the morale of Lashkar and other Kashmiri jihadi groups and to stop growing integration between Kashmiri Jihadist groups and "Taliban-based outfits." Several of these groups were identifying more with the Taliban's jihadist activities in Pakistan and Afghanistan and the ISI wanted to shift "the theater of violence from the domestic soil of Pakistan to India."

"The aggression and commitment to jihad shown by several splinter groups in Afghanistan influenced many committed fighters to leave [LeT to join these organizations]," Headley said. "I understand this compelled the LeT to consider a spectacular terrorist strike in India."

The report detailed meetings Headley held with members of the Pakistani intelligence agency. He also claimed to have received $25,000 from his ISI handler to finance a reconnaissance trip to India.

Headley also confessed to interrogators about a plan to attack high-profile targets in Delhi, including the prime minister's residence and the premier National Defense College.

The Pakistani government has denied news reports of ISI involvement in the attacks and an ISI spokesperson called the allegations as "baseless."