Who is Azam Amir Kasab? And, more to the point, where did he come from?

Indian interrogators hope to solve the puzzle over the identity of the sole Islamic militant captured during the terror attacks in Mumbai last week by administering a “truth serum”.

The mystery of the man dubbed “the baby-faced gunman” has weighed heavily on India’s relations with Pakistan as the nuclear-armed neighbours dispute each other’s accounts of his origin, and the United States tries to avert a war between them.

Police interrogators in Mumbai told The Times that they were poised to settle the matter of Kasab’s nationality through the use of “narcoanalysis” – a technique banned in most democracies – where the subject is injected with a truth serum.

According to police Kasab had identified himself as a 24-year-old Pakistani from the village of Faridkot in the southern part of the Pakistani province of Punjab. “We have verified, cross-checked this,” said Deven Bharti, a deputy police commissioner in Mumbai and one of the interrogators. “We know his father owned a food stall there.”

He painted a picture of a poor village boy who failed to complete primary school but went on to undertake up to 18 months of military training at militant camps in Pakistan.

“He is a 24-year-old boy with the eyes of a killer,” Mr Bharti said. “Nobody should doubt: he is a highly trained murderer. He has told us he came to Mumbai from Pakistan to cause maximum casualties.”

He said that Kasab and the nine gunmen who were killed in the attacks had been chosen from a group of twenty-four who had gone through the same extensive training, overseen by an ex-army officer. They were prepared by being shown violent foot-age from Iraq, Afghanistan and Palestine.

Evidence of a Pakistan link also includes grenades found on the gunmen which were manufactured in Pakistan, and satellite telephone calls from a handset used by the militants, according to Indian police.

Indian investigators said yesterday that 8kg of explosives had been found in a bag in the main Mumbai railway station, where Kasab and an accomplice killed 56 people.

Asked for further details of the evidence Mr Bharti said: “What do you need? He is living evidence.”

Pakistani officials, however, told The Times that they could find no trace of a person fitting the description of Kasab, and said that there were three villages called Faridkot in Punjab and they did not know to which one the Indian authorities were referring.

All three are now swamped with Pakistani intelligence agents and reporters, to the consternation of the locals. “We don’t know anyone by this name, but they keep harassing us,” said Mohammed Bilal, a farmer in one of the villages called Faridkot, 30 miles (48 kilometres) from the city of Multan.

Southern Punjab is one of the poorest regions in Pakistan and a fertile recruiting ground for Islamic militant groups, but locals in this Faridkot said that no one they knew had links to such groups. A senior Pakistani security official said that there was no evidence that Kasab came from there.

It was the same story in another Faridkot, about 40 miles away in Khanewal district: militant groups have been active in the area, but intelligence officials say there is no trace of Kasab or his family. “We have become very worried. What’s this all about?” a villager said.

The debate over Kasab’s identity threatens to undermine US efforts to get India and Pakistan to cooperate in investigating the attacks.

Condoleezza Rice, the US Secretary of State, met Indian leaders in Delhi to urge them to show restraint in their response to the attacks, which they blame on Pakistani militants.

US Admiral Mike Mullen, Chairman of the Joint Chiefs of Staff, also met Pakistani leaders in Islamabad to press them to cooperate with India’s investigation and not to pull back troops fighting Islamist militants on the Afghan border.

Their diplomatic efforts were undermined, however, when Asif Ali Zardari, Pakistan’s President, refused India’s request to extradite 20 terror suspects and said that he doubted Delhi’s claim that Kasab was from Pakistan. “We have not been given any tangible proof to say that he is definitely a Pakistani. I very much doubt it,” he told CNN.

His remarks will have infuriated Indian officials, who told Dr Rice that the attacks were carried out by the militant group Lashkar-e-Taiba, which is based in Pakistan. Public anger was also building last night as hundreds of Mumbai residents protested, demanding that Pakistan should be declared a terrorist state.

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