China's Olympic gold medal-winning hurdler Liu Xiang, one of the country's biggest sports stars, has retired.

The 31-year-old won the country's first Olympic men's athletics gold in the 110m hurdles in Athens in 2004 and added a world title in 2007.

He also held the world record in 2006 with a time of 12.88 seconds.

"I'm retiring. I want to start a new journey," Liu said in a message posted to his blog, blaming injury for his decision.

Liu has been affected by an Achilles problem ever since it caused him to pull out of his first heat at the 2008 Beijing Olympics.

He then had surgery after crashing out of his heat at London 2012.

Liu is held in the same high esteem in China as popular basketball player Yao Ming and tennis star Li Na, who have also recently retired.

He made millions of pounds from sponsorship deals with the likes of Nike and Coca-Cola.