An undated photograph in the early 1980s provided by judo coach Jimmy Wu shows what Wu says is Osama Bin Laden dressed in his judo gi in Riyadhin, Saudi Arabia, according to Wu on May 7, 2011. [Photo/Agencies]

Osama bin Laden stood out not just because of his height but because of his serious, conservative demeanour, according to a man who says the al-Qaida leader, killed by US troops on Monday, was a student in his judo classes in Saudi Arabia.

Special coverage:  US kills bin Laden

Jimmy Wu, a judo coach, told Reuters in an interview on the sidelines of a tournament in the central city of Taichung that he came across bin Laden when coaching the Saudi Arabian national judo team from 1981 to 1991.

Bin Laden, whom Wu then knew only as "Osama", attended classes at the judo centre while still a university student. He was too tall for judo, and Wu said he advised him against the sport, but he was insistent so Wu accepted him.

"I didn't know the name bin Laden then," Wu said. "After 9/11 (attacks on New York and Washington), I was invited to a seminar, and some of my former students there said 'oh Jimmy, Osama, now he's our hero'. I was surprised and I looked for some pictures and I said 'oh this guy' and I started to have some memory of him."

Wu showed Reuters photographs of himself and a tall, thin, bearded, serious young man with a mop of black hair whom he said was Osama. Osama attended lessons two to three times a week but Wu never saw him again after 1984.

Reuters has no way of verifying that the man in the pictures was bin Laden.

Bin Laden was shot dead by US forces in Pakistan on Monday. He had been on America's most wanted list since his followers carried out the Sept 11 attacks on the World Trade Center in New York in 2001.

Pakistan officials said on Saturday that he may have lived in the country for seven years.

Wu, now an Australian citizen who divides his time between Sydney, China's Taiwan and the Middle East, remembered an occasion when his wife came to find him at the judo centre. She had wanted to go shopping and Wu was late.

"She came into the centre and most of the students weren't bothered, some smiled, but one really tall guy came to me and said 'who is that?'"

Wu replied that it was his wife. "The tall one said 'this is the centre, no women should be in here'. He did not approve. I have a particular memory of this. That was Osama."