"We hope he will take proper rest and focus on his recovery. We hope that after he recovers, he will continue to train hard and struggle harder for national glory."

Liu said he would cooperate with doctors and try to return to the tracks as soon as possible.

Why is Liu Xiang so important? He is the first Chinese, indeed the first Asian man, to win a gold in an Olympic track event. He proved his Athens win was no flash in the pan by bettering the world record later. And he had the chance to defend his title at home.

The ace hurdler outlined his plan for the next four years after winning the gold in 2004. His was a plan with its route clearly mapped out. A gold in the 110m hurdles final at the Bird's Nest on Thursday night was his goal - and that of China's 1.3 billion people.

A spectator reacts after China's Liu Xiang failed to compete in the men's first round 110m hurdles heat 6 at the "Bird's Nest" National Stadium during the 2008 Beijing Olympic Games on August 18, 2008. [Agencies]

He may return to the London Olympics in 2012. He may regain the world record. Or, he could win the world title next year. But neither he nor anyone else can make up for Monday's loss.

Feng Shuyong, head coach of China's athletics team, however, said at a press conference: "Liu has a strong will (he can) fight till the last minute if his injury hadn't been so serious, he would never have withdrawn from the race."

Liu's coach Sun Haiping, who broke down at the press conference, explained that the hurdler suffered an injury in the Achilles' tendon more than six years ago but it worsened during training on Saturday.

"Liu's heel bone is different from others and so his Achilles' tendon is more vulnerable, but we had taken care of the pain properly before. It didn't hurt him till Saturday," Sun said.

"Liu insisted on running at the Beijing Games. Before the warming up for the race, three doctors tried their best to ease the pain but it didn't subside. Even then Liu decided to run, risking his career ."

Feng, who said he was the "best witness of the painful road Liu had undertaken", praised the hurdler for his strong mind and positive spirit. "Liu was in very good form before Saturday."

His strongest rival and current world record holder, Cuba's Dayron Robles, regretted the loss of his arch rival in the competition.

"I'm sorry for him," Robles told China Daily, "because he is a big athlete, and a big rival for everybody. He is a good man." Robles, who broke Liu's world record in June, cruised into the second round of the heats by finishing first earlier in the day.

Officials of the sports governing body, the International Association of Athletics Federation (IAAF) have expressed shock too.

"It's a huge shock. He deserves great support from all the others at this moment," Anna Legnani, IAAF deputy communications director, said.