In the last heat of the first round, Liu quit after someone else false-started. He then limped into the tunnel, leaving the 60,000-plus spectators at the Bird's Nest stadium and millions of home audience watching in front of television in shock.

"Liu was depressed," said Chinese athletics head coach Feng Shuyong. "He was very sad about the result."

"If his injury hadn't been so serious, he would never, ever have quit the race."

Liu's coach, Sun Haiping, couldn't control his emotions at a press conference held shortly afterwards, choking on every answer to reporters' questions.

"He has been fighting until the last moment," said Sun.

Even before the 110m hurdles race Liu was seen on television clutching his right foot after attempting just two hurdles during warm-up.

Liu has been touted as an icon of China's sport since he equaled Colin Jackson's world record of 12.91 seconds to win the 110m hurdles in Athens four years ago. He went on to break the world record by clocking 12.88 seconds at an IAAF meet in Lausanne, Switzerland in 2006, and grab his first ever world championship title in Osaka in 2007.

No other Chinese athlete has carried heavier burden of expectations into the Beijing Games than Liu. But the 25-year-old has been struggling with leg and tendon injuries since the beginning of this year, and the rise of a formidable rival - Cuban Dayron Robles - has made Liu's title-defending campaign even more arduous.

Liu lost his world record to Cuban Dayron Robles, who finished a race in 12.87 seconds in June.

Luo Ming, who calls herself "an avid Liu fan" and came from east China's Zhejiang province to watch Liu's first outing in the Bird's Nest stadium, said she was shocked at Liu's sudden withdrawal but will always be a Liu supporter.

"I was stunned. I don't know what to say," said the 23-year-old accountant. "But I will always support him. He remains my biggest idol."

Earlier, Robles won his heat in 13.39 seconds to go through. Now he is the overwhelming favorite for the coveted gold.

Despite Liu's shock exit, China's gold juggernaut kept rolling. Two gold medals in gymnastics, one apiece in table tennis and trampoline lifted its total to 39, seven more than its previous best of 32 in Athens and well ahead of the United States (22).

Chen Yibing led a 1-2 Chinese finish in the men's rings, beating compatriot and newly-crowned all-around Olympic champion Yang Wei.

He Kexin of China and American Nastia Liukin both scored the highest mark of 16.725 points on the women's uneven bars, but a tie-break rule based on an analysis of the judges' individual scores placed He first. China's Yang Yilin took bronze on 16.65 points.

"I didn't expect to win the gold because the more I want, the more pressure I feel," said He.

Liukin, who won the individual all-around gold last Friday, admitted that she was confused about the rule.

"I honestly was in shock," said the 19-year-old Liukin. "I knew I didn't have my best routine (but) when I saw we got the same score and my name was second, it was weird."

But she was quick to console herself.

"It's nothing I can control, and honestly, I can say it has been very fair to me. I got the biggest gold medal of them all," said Liukin, referring to her all-around title.

The Chinese trio of Ma Lin, Wang Hao and Wang Liqin crushed Germany 3-0 to win the men's team table tennis final, and He Wenna of China took the the women's trampoline title.

Hours after Liu Xiang's shock withdrawal, Russia's Yelena Isinbayeva, dubbed the female Sergei Bubka, took center stage at the Bird's Nest as she broke her own world record to win the women's pole vault gold.

Isinbayeva's first attempt over 4.85m was already good enough to secure the gold. She needed three attempts to clear 5.05m, eclipsing the previous world mark by one centimeter.

After the historic attempt, the 26-year-old did a forward somersault on the mat. She then draped herself in a Russian flag, ran a lap of honor and waved to the spectators in the stands.

Isinbayeva has broken the world record for 24 times. She has stated her career goal is to beat Ukrainian great Sergei Bubka's mark of 35 world records.

Stephanie Brown Trafton earned the United States its first athletics gold of the Games when she won the women's discus throw with a best effort of 64.74 meters.

The Americans then made a clean sweep of medals in the men's 400m hurdles with Angelo Taylor taking gold in 47.25 seconds.

Kenya's dominance of the 3,000m steeplechase continued as world champion Brimin Kipruto clocked 8 minutes 10.24 seconds to win the event. It was the African country's seven consecutive steeplechase titles since the Los Angeles Games in 1984.

Pamela Jelimo, also from Kenya, then won the women's 800m in 1:54.87 to give her country second gold of the games, while Irving Saladino of Panama took the men's long jump title with a leap of 8.34 meters.

Australia's Emma Snowsill, three-time world champion, ran away with the women's triathlon gold medal, with current world number one Vanessa Fernandes of Portugal taking the silver and another Australian, Emma Moffett the bronze.

Snowsill broke away from her Portuguese rival after the start of the 10km run, and she eventually finished just over a minute ahead in a time of 1 hour 58 minutes 27.66 seconds.

The Australians made a golden double in sailing with Nathan Wilmot and Malcolm Page winning the men's 470 sailing event and Elise Pechichi and Tessa Parkinson prevailing in the women's 470 competition.

Britain smashed its own world record to win the men's team pursuit cycling gold in 3 minutes 53.314 seconds, and Dutchwoman Marianne Vos added the Olympic crown to her world championship title when she outrode Yoanka Gonzalez of Cuba and Leire Olaberria of Spain in the women's points race.

NBA star Yao Ming scored 18 points and grabbed five rebounds in 18 minutes but it was not enough to prevent China from losing 91-77 to Greece in its final Group B match of the men's basketball tournament. China, who finished fourth in the group, will face Lithuania in the quarterfinals on Wednesday.

In soccer, the Brazilian women's team took a sweet revenge on Germany by routing the World Cup champion 4-1 to reach the final. Germany downed Brazil 2-0 in last year's World Cup final.

The United States beat Japan 4-2 in the other semifinal.