Jamaican sprint king Usain Bolt paid tribute to Liu Xiang on Tuesday after the Chinese star suffered an agonising exit from the Olympics for the second time in a row.

Liu, who had been forced to withdraw from the 110m hurdles in Beijing four years ago just moments before his first heat, fell at the first hurdle here Tuesday as he returned to the Olympic arena.

The 29-year-old’s sad exit from the c o m p e t i t i o n sparked a wave of sympathy amongst athletes and spectators, wilh 100m champion Bolt leading the way.

"It is really hard for him because I think he is one of the best, hands down," said Bolt after strolling through his opening 200m heat.