LONDON, July 31: China’s teenage swimmer Ye Shiwen overcame doping allegations on Tuesday as she won gold in the women’s 200m individual medley while American Michael Phelps equal an all-time Olympic medal record.

China extended their lead at the top of the medals table with 12 golds ahead of the United States who have eight.

On a day which opened with China vehemently rejecting suggestions by an American coach that doping might be behind the astonishing performance of Ye, who won Saturday's 400 metre individual medley by slashing more than a second from the world record, Chinese fencer Lei Sheng also won gold in the men's individual foil.

Lei Sheng beat Alaaeldin Abouelkassem of Egypt 15-13 in Tuesday's final with the Egyptian becoming the first African fencer to win an Olympic medal.

But the day fittingly belonged to Ye who romped to victory in the 200m final after doping claims.

American John Leonard, executive director of the World Swimming Coaches Association but not on the US coaching staff in London, told Britain's Guardian newspaper: “Every time we see something ... 'unbelievable', history shows us that it turns out later on there was doping involved.”

However China's authorities went on the offensive at Ye's critics on Tuesday, while a slew of Olympic swimming greats, coaches and officials also lined up in support of the 16-year-old sensation.

“The Chinese athletes, including the swimmers, have undergone nearly 100 drug tests since they arrived here,” Jiang Zhixue, the head of anti-doping at China's General Administration of Sport, told Xinhua news agency.

Ye took the lead in the final lap and clocked 2 minutes, 7.57 seconds, shaving 0.18 off her own mark set in Monday's semi-final.

Alicia Coutts of Australia touched in 2:08.15 to take the silver medal and Caitlin Leverenz of the United States finished in 2:08.95 to take bronze.

Earlier, Phelps failed by a finger tip to become the first male swimmer to win the same event at three successive Olympics when he was pipped to gold in the 200 metres butterfly, but the silver he won saw him equal the all-time record of 18 medals.

The American swimmer led going into the last few metres of his favourite race, but was tiring rapidly and had to settle for second when South Africa's Chad Le Clos ploughed through to snatch it on the final touch.

Watching at poolside was Larisa Latynina, the Soviet gymnast who has held the record for decades with her haul — including nine golds — from the Games at Melbourne (1956), Rome (1960) and Tokyo (1964).

Better news for America came when Allison Schmitt claimed an Olympic record to win the gold medal in the women's 200m freestyle.

Schmitt went one better than her silver medal in the 400m freestyle earlier in the Games to score a clear-cut victory in one minute 53.61 seconds.

In other action on day 4 of the Games, the Americans opened the women's team gymnastics competition with a barrage of booming vaults to grab their first gold since 1996.

The Russians cried on the sidelines as the US gymnastics team scored a comfortable victory. The Americans had come into the last two Olympics as world champions, only to leave without a gold.

China leads the overall medal table ahead of the United States and France.

In tennis, Serena Williams was not selected to play in mixed doubles, while her sister Venus moved into the third round after beating Aleksandra Wozniak of Canada 6-1, 6-3.

Andy Roddick played his last day at the Games after losing the second round 6-2, 6-1, to Novak Djokovic of Serbia. British hopeful Andy Murray, seeded third, advanced by beating Jarkko Nieminen of Finland 6-2, 6-4.

Olympic tennis also saw a new record when Jo-Wilfried Tsonga of France defeated Milos Raonic of Canada, 6-3, 3-6, 25-23. The previous record was 30 games, set in 2004.

There was good news for the host country as British rower Alan Campbell qualified fastest for the semi-finals of the men's single sculls.

Reigning two-time champion Olaf Tufte of Norway also squeezed into the semi-finals by placing third in the last quarter-final.

There was good news for one of Saudi Arabia's two first female Olympians when their judoka Wojdan Ali Seraj Abdulrahim Shahrkhani was given the go-ahead to compete in the women's heavyweight division on Friday wearing a hijab.

The Saudis had threatened to pull the fighter out of the Games if she was forced to compete with her head uncovered before a compromise was found.

But judo officials had initially said a headscarf could be dangerous because the sport includes chokeholds and aggressive grabbing techniques.

A Saudi National Olympic Committee spokeswoman said the committee, the IOC and the International Judo Federation had agreed on an acceptable form for the headscarf.—Agencies