Fresh evidence has been uncovered linking Khan to Omar Sharif and Hanif Asif, who killed three people and injured 50 in 2003 with a suicide attack on a bar in Tel Aviv.

According to a witness who has not yet spoken to the police, the men wanted to indoctrinate young Muslims and take them abroad for further training.

Kursheed Fiaz, a businessman who runs an information technology company in Manchester, had four or five meetings with Khan who was initially accompanied by Sharif and later by Asif.

The close link between the two groups of suicide bombers suggests Britain’s Islamic terror network may be more tightly knit than previously thought.

It also raises questions as to whether Khan may have been involved in the Tel Aviv bombing. Israeli police have confirmed that Khan visited Israel on February 19, 2003, two months before the attack.

Accompanied by a group of British tourists and a woman said to be his wife, Khan spent only 24 hours in the country. Israeli authorities have investigated the trip but have been unable to establish whether it might have been a “dry run” or reconnaissance mission for the bombers.

The new evidence — to be broadcast on a BBC2 programme on Tuesday — could also prove useful to police in Britain. Anti-terror squad detectives have been attempting to build a profile of Khan, the ringleader of the four London suicide bombers who killed 52 people on three Underground trains and a bus last year.

According to the official government report into the London bombings, Khan had a westernised upbringing but his outlook began to change in 2003 when he made friends with a group of radicals from Leeds and Huddersfield. Previously apolitical, he became enraged about Muslim suffering around the world after watching hardline Islamic videos.

But Fiaz’s account suggests that he may have become radical much earlier. Fiaz says he was contacted by Khan in the summer of 2001. Khan had taken a job as a primary school assistant in Beeston, Leeds, a few months earlier.

Fiaz, 46, is originally from Jhelum in northern Punjab, where Asif’s father also grew up. It is thought Asif may have recommended Fiaz to Khan as an influential businessman.

According to Fiaz’s account, Khan came to his office seeking to spread “Dawa” — a form of evangelical preaching that is common in the Islamic world. It is mostly benign but can also be an essential step in the development of a young militant.

Khan was accompanied by Sharif and an unidentified man. Sharif, then aged 25, had recently returned from studying Arabic in Damascus.

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