31 July 2012 Last updated at 02:34 ET

China's 16-year-old swimming star Ye Shiwen has denied taking performance-enhancing drugs after smashing a world record at the London Olympics.

She spoke out after a leading US coach described her performance in the 400m individual medley as "disturbing".

Ms Ye swam the 400m individual medley seconds faster than she ever had before and - on the last 50m - faster than the winner of the men's event.

There is no evidence against her and all medal winners are drug-tested.

On Monday, Ye Shiwen took at least five seconds off her personal best to break the world record by more than a second and win the gold medal in the individual medley.

In the last 50m she swam faster than US star Ryan Lochte in the men's event.

Commentators were stunned, including the BBC's Clare Balding who said questions would be asked about the swimmer's performance.

American coach John Leonard, executive director of the World Swimming Coaches Association, said her performance was "unbelievable" and "disturbing".

"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," he told the UK's Guardian newspaper.

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China swimming star denies doping