Japanese men's backstroke swimmer Junya Koga, a member of the 2016 Rio de Janeiro Olympic team, denied on Wednesday taking banned substances following an announcement he had failed a doping test.

"This is unbelievable," the 30-year-old said at a press conference after the Japan Swimming Federation announced he had failed a test.

"Because my thinking on doping has been very strict all this time, I feel it's pathetic, shameful and also frustrating that a prohibited substance has come from my own body," he said.

The International Swimming Federation has handed Koga a provisional suspension, and he has been pulled from Japan's team for the Asian Games starting in August in Jakarta. According to his agent, Koga's urine samples taken in an unscheduled March 2 out-of-competition test, contained a prohibited anabolic agent used to build muscle. The backup sample also tested positive.

Koga's side is asserting there is a strong possibility the banned substance was included in supplements he took. Koga, who does not have a history of violations, will seek leniency from the swimming federation, which can suspend him for four years.

After not being selected for the 2012 London Olympics, Koga, the 2009 world champion in the 100-meter backstroke, was picked for the Rio Games as a member of the 4x100 medley relay team.

(Junya Koga wins the men's 100m backstroke at the world c'ships in Rome in July 2009)