Japan's national women's judo head coach said Thursday he would resign, the day after allegations emerged he had beaten his athletes with wooden swords.

Ryuji Sonoda said that in the wake of the allegations it would be "difficult" for him to stay as coach, a position that sees him training Olympic athletes.

"I would like to deeply apologise for causing trouble to all the people concerned with what I have done and said," Sonoda told a news conference.

"I think it will be difficult for me to continue being engaged in the training programme any longer. I wish to submit my resignation."

On Wednesday it was widely reported that a 15-strong group of judokas, including some who took part in the London Olympics, had complained to the Japanese Olympic Committee that they had been physically abused.

They said they were beaten with thick bamboo swords, like those used in the Japanese martial art of kendo, and were slapped by their coaches.

They also complained that some were forced to compete in matches while injured, reports said.

At Thursday's news conference, a contrite Sonoda made a deep bow of apology and admitted the allegations were "more or less true".