Japan's rugby body said on Wednesday it had suspended World Cup hopeful Ryohei Yamanaka for two years for using a banned substance which he blamed on a cream to help him grow a moustache.

The 23-year-old one-cap fly-half tested positive in a random doping check in April during a training camp ahead of the Asian Five Nations tournament, and a follow-up test showed the same result.

The International Rugby Board ruled that the substance was a steroid, either methyltestosterone or methandriol, said the Japan Rugby Football Union (JRFU).

The Kobelco Steelers rookie told rugby authorities that he thought the cream was a cosmetic product that did not contain banned substances, the JRFU said.

Yamanaka, who left the Steelers on Wednesday, said he hoped to return to the game after the suspension.

"It is regrettable that a Japan international was suspended from competition for violation of anti-doping regulations," said JRFU chairman Tatsuzo Yabe.

"The player and the Japan Rugby Football Union solemnly accept the ruling," he said, adding that the union would make further efforts to educate players about doping rules.

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