A Chinese teen swimmer's astonishing performance at the London Olympics has raised eyebrows as most senior swimming coaches expressed suspicion over her performance. Chinese officials, meanwhile, rejected the allegations as baseless.

Ye Shiwen, the 16-year-old Chinese swimmer won the gold in the women's 400m individual medley, clocking an unbelievable 4:28.43 and setting the first world record at the London Olympics. Ye finished the final lap faster than the same lap performance of the American swimmer Ryan Lochte who won the gold in same category in the men's event.

However, her remarkable performance has become first controversy at the London Olympics as one of the most respected senior swimming coaches, John Leonard, expressed doubts over her performance, calling it "unbelievable," The Guardian reported.

Leonard, the executive director of the World Swimming Coaches Association, compared her performance to that of Irish swimmer Michelle Smith's gold-winning performance in the same event at the 1996 Atlanta Olympics. Smith, now Michelle de Bruin, was accused of tampering with the urine sample and was banned for four years in 1998 after testing positive for an anabolic steroid.

Leonard termed Ye's performance as "suspicious" and "unbelievable." "We want to be very careful about calling it doping," he said.

"The one thing I will say is that history in our sport will tell you that every time we see something, and I will put quotation marks around this, 'unbelievable', history shows us that it turns out later on there was doping involved. That last 100m was reminiscent of some old East German swimmers, for people who have been around a while. It was reminiscent of the 400m individual medley by a young Irish woman in Atlanta," said Leonard, according to the Guardian report.

Many other gold medal-winning swimmers and coaches have also described Ye's performance as "insanely fast," "amazing" and "unbelievable."

Ye and China hit back at the allegations saying that there was no proof against her and that all the medal winners were tested for drugs.

"My results come from hard work and training and I would never use any banned drugs. The Chinese people have clean hands," Ye told reporters, reacting to the suspicions.

The leader of the Chinese swimming team, Xu Qi, also remarked that to "compare Ye's result with Lochte's is meaningless, as Lochte had already established a clear lead by the third lap, while Ye who was behind had to put her best effort to win the game," the Chinese news agency reported.

"Michael Phelps won eight gold medals at the Beijing Games ... and American swimmer Missy Franklin is also incredible ... Why can't China have a talented swimmer?" Xu Qi said.

All the medal winners in the Olympics are tested for drugs and incredible performances attract extra tests for doping.