CHINA's Olympic champion Liu Xiang failed to start his 110 metres hurdles first-round heat today.

China's Olympic gold medal-winning hurdler Liu Xiang announced his retirement on Tuesday, ending a run in the sport marked by records and frustrated by successive late-career injuries.

Defending Olympic champion Park Ta-Hwan was leading at the final turn, but the 20-year-old Sun surged past his South Korean rival in the final length to seal a place in Chinese Olympic history.