Japan swimmer Koga axed after failed drugs test

Former swimming world champion Junya Koga has been kicked out of the Japan squad for this summer's Asian Games after failing a drug test, officials said Wednesday.

The 30-year-old, who won the 100 metres backstroke world title in 2009, tested positive for traces of banned muscle-building substances, according to the Japan Swimming Federation (JSF).

Koga denied taking the substances knowingly but admitted taking a diet of supplements which could have been to blame. He now faces a maximum ban of four years.

"I feel ashamed, miserable and frustrated," the swimmer told a news conference.

"I couldn't believe it -- I was in shock, I thought it was some mistake," added Koga, who failed a test conducted by the World Anti-Doping Agency (WADA) in March.

"I didn't know if it was real, or a dream. I never took the substance detected intentionally. But I'm responsible for proving that. To those who support me, I'm deeply sorry."