The FBI has cleared Pakistan Inter-Services Intelligence (ISI) of any involvement in last month's terror attack on India's financial hub.

After interrogating the sole surviving gunman, The Federal Bureau of Investigation (FBI) concluded that the ISI was cleared of any involvement in the Mumbai terror attacks on November 26, Pakistani daily The Dawn quoted diplomatic sources as saying on Thursday.

Pakistani Mohammed Ajmal Amir Qasab was among a group of 10 armed men who went on a shooting rampage in more than 10 sites, including two luxury hotels, in Mumbai.

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Citing other sources, The Dawn said investigations had also revealed that the attackers had crossed the border from Pakistan, where the well-orchestrated plot was sketched by the Lashkar-e-Taiba (LeT).

The ISI was accused of being involved in the Mumbai attacks due to its past associations with the LeT, which received CIA and ISI support to fight the soviet-backed government in Afghanistan.

The CIA had built extensive bases for the LeT in Pakistan and Afghanistan to train thousands of guerrilla fighters, according to Frontline magazine.

Pakistani President Asif Ali Zardari has repeated asked India for concrete proof implicating the LeT in the attack, as tension between the two neighbors intensifies.

The nuclear-armed nations already have a history of three wars since independence from Britain in 1947.