LONDON - Italy's reigning 50km walk champion Alex Schwazer admitted doping on Monday and said his career was over after he was withdrawn from the Olympics for failing a drugs test.

"My career is over. I made a mistake. I wanted to be stronger for this Olympics, I was wrong," Schwazer told Italy's ANSA news agency.

"I take full responsibility for what has happened. I did it by myself, it was my idea.”

A source with knowledge of the case said Schwazer, 27, had tested positive for the banned blood booster EPO during a test conducted by the World Anti-Doping Agency (WADA) at a training camp in Oberstdorf, Germany.

The Italian Olympic Committee (CONI) said in a statement an athlete had been withdrawn from the Olympics for failing a drugs test but did not name the athlete or the sport.

"The president of the Italian Olympic Committee (CONI), Giovanni Petrucci, having spoken to the head of the (Olympic) delegation, Raffaele Pagnozzi, has immediately excluded from the Olympic team an athlete who had not yet gone to London," said the CONI statement.

"This afternoon CONI received a notification of an adverse finding from WADA in an anti-doping control taken by this athlete.

"The head of the relevant discipline has promptly informed by CONI about the decision."

Schwazer was a bronze medallist at the 2005 and 2007 World Championships before striking gold at Beijing four years ago.

He had been one of Italy's best medal hopes in London after a solid start to the season which saw him clock the fourth best time of his career.

WADA has warned the London Games would see the most rigorous testing regime in history, with more than 6,000 tests expected to be carried out during the fortnight-long sporting extravaganza.

(AFP)