Japan's Education Minister was less circumspect, calling on sumo officials to give a full explanation.

'The association has a responsibility to explain it as the case is of major public concern,' Kisaburo Tokai told reporters.

'I want them to deal with it properly to win back the association's honour and meet the expectations of fans.'

Sumo officials kept their counsel after the arrest, with JSA chairman Kitanoumi saying only that it was 'extremely regrettable for the long history' of the sport.

Japanese media roundly condemned the closeted world of sumo in Friday's editorials after 'stable master' Tokitsukaze, 57, and three wrestlers were arrested in Aichi, central Japan.

'This is a grave incident which disgraces the history of sumo,' the Nikkei business daily said, while the Asahi newspaper suggested that the JSA was 'disintegrating'.

'Preventative measures'
Japan's conservative Yomiuri newspaper called on sumo elders to clean up their act.

'The Sumo world must take preventative measures,' the mass-circulation daily said in its editorial. 'Harsh training is needed to nurture strong wrestlers. But violence in the name of training is unforgivable.'

Local media reported that Tokitsukaze, whose real name is Junichi Yamamoto, had instructed senior wrestlers to beat up the novice wrestler during sparring practice last June.

The teenager, Tokitaizan, died a day later. The sumo association initially said he had died from heart failure.

But Tokitaizan's father said there were bruises on his son's body and what appeared to be burns. Media reported that autopsies carried out recently showed the wrestler died from multiple traumatic shocks.

Former wrestlers have said newcomers are often put through brutal 'character-building' training sessions at the sumo stables where younger wrestlers eat, sleep and train together.

Tokitaizan, whose real name was Takashi Saito, had twice fled from the stable, complaining of a lack of privacy, his father had also said.

'Certainly training can be harsh in various sports but if it's excessive, it will lead to such incidents,' Chief Cabinet Secretary Nobutaka Machimura told reporters.

'It is truly deplorable because violence was allegedly carried out in the name of exercise.' -- REUTERS