BEIJING, AP:

FORMER Olympic champion hurdler Liu Xiang confirmed his retirement on Tuesday, citing age and injuries two and a half years after his last race.

The 31-year-old Liu wrote in a lengthy statement on his microblog titled 'My Track, My Hurdle' that he was "truly unwell and old and can no longer run and jump with you".

"Although it's sad, although it's painful, I really have no other choice," Liu wrote.

Liu became the first Chinese man to win Olympic gold in athletics at the 2004 Athens Games in the 110-metre hurdles, in a then-world record time. He set another world record in 2005, and won at the world championships in 2007.

The Shanghai native hasn't competed since withdrawing at the London Olympics in 2012 after rupturing his Achilles tendon.

He pulled out of the 2008 Beijing Games with a similar injury, and years of treatment have apparently failed to fix the problem.

Given his experiences at the Beijing and London Games, Chinese sports officials said Liu would not return to competition before making a full recovery. However, Achilles injuries are difficult to heal, and many sprinters never return to their previous best.

In his statement, Liu said he hoped to recover after London, but "my foot told me no again and again, and there was no way it was going to be able to handle intense training and competition.

"I hate my foot, I love my track and my hurdle so much, and if I hadn't injured my foot ... but then there are no 'ifs' in this world, I injured myself, and can only accept it silently."

Over his career, he became one of China's highest-earning sports stars, joining the elite ranks of former NBA star Yao Ming and tennis champion Li Na.

Liu's plans to retire had been long expected, and were reported by a Shanghai newspaper last week.