Phelps wins 21st medal as US overtakes China

Guo Shuang gave China second silver medal in cycling events when she was narrowly beaten by Briton Victoria Pendleton in the women's keirin, a day after she and teammate Gong Jinjie won the team sprint event only to be relegated soon after an "illegal changeover".

Germany's Miriam Welte and Kristina Vogel were crowned inaugural Olympic women's team sprint champions following the relegation of China.

But the Chinese cycling team appealed the ruling on Friday. In an official statement, the Chinese team said: "Gong Jinjie and her teammate Guo Shuang beat the record twice, in the qualifying and the first round. In the final, Chinese team beat Germany with a result of 32.617, but was relegated to second place by the referee who did not show any video replay."

"Our gold was robbed," China's French coach Daniel Morelon said on Friday. "Even if there is no appeal process in cycling, we still wanted the world to know that this is unfair and shameful for the Olympic spirit," he said.

"After the race, I came to the referee, who did not show me any video replay," said Morelon, a cycling legend who won four Olympic golds in his career.

"I watched the race video again and again, after I returned to the Athletes' Village. I looked over the rules and regulations of the sport and concluded the Chinese didn't violate any rules."

On the first day of athletics action, Poland's Tomasz Majewski clinched the men's shot put gold with a throw of 21.89 meters. Germany's David Storl claimed silver with 21.86m and American Reese Hoffa bronze with 21.23.

Ethiopia's Tirunesh Dibaba became the first woman to win the Olympic 10,000m final for the second straight time. She crossed the line in 30 minutes 20.75 seconds, a world best time for 2012.