Hashimoto, an Olympian in speed skating and cycling, said, "I was very sad to hear this news. 

"We were teammates in Seoul, Barcelona and Atlanta.

"He was a great athlete during his time at the Olympics.

"He had a lot of passion for his sport."

In 1992 Koga was the reigning world lightweight - under-71 kilograms - champion and a firm favourite for gold but had injured his knee in a training bout before the Barcelona Olympics.

He overcame the injury to defeat Hungarian Bertalan Hajtós in the gold-medal bout.

Hashimoto added, "I remember the moment he won. 

"He had told me that despite the injury he was going to win gold. 

"I very much respected his strength."

Koga retired after the Games but returned to compete in Atlanta at the centennial Games where he won under-78kg silver.

Koga three world titles in all, at both under-71kg and under-78kg. 

He remained in the sport as a coach to the Japanese team. 

Among his charges was Ayumi Tanimoto who won wonen's under-63kg gold at Athens 2004 and Beijing 2008.

"People like Koga-san lead the next generation so I really regret his passing," said Hashimoto.

Koga was to have been a Torchbearer in Saga prefecture where the Olympic Flame is due on May 8 and 9.

He had been hospitalised with cancer last year but died at his home in Kawasaki, near Tokyo.

The International Judo Federation posted its own tribute which ended with the words "thank you to the artist".

His fellow Barcelona gold medallist Hideko Yoshida told Nikkei Asia: "I’m still in a state of disbelief. 

"When Koga won at the Barcelona Olympics, I felt more joy than when I won myself. 

"That both of us won gold medals is something I treasure."