TOKYO — Three sumo wrestlers and a former instructor went on trial today for allegedly beating a younger wrestler to death during training last year.

Seventeen-year-old wrestler Tokitaizan, whose real name was Takashi Saito, died June 26 after he collapsed following practice. An autopsy showed bruises and wounds on his body that did not appear consistent with sumo training.

Today, the three wrestlers admitted in court they had beaten Saito and said they had been unable to refuse orders to do so by their stable master, according to news reports. A court spokesman refused to confirm the reports.

The Japan Sumo Association fired the stable master and instructor Tokitsukaze last year, an extremely rare move, although he was facing no criminal charges. He has acknowledged he struck Saito on the head with a beer bottle the day before he died, and forced him to train so hard that he could barely stand on the day of his death.

In the rigid, traditional world of sumo, young recruits join a stable, which becomes responsible for almost all aspects of their training and welfare. A tiny percentage become professional fighters, and many drop out due to the rigorous training and harsh living conditions.

Masato Saito, the boy's father, has said that his son fled the stable twice, including once on the day before his death, but was returned each time.

"I just want them not to hide anything, and to tell the truth," he told reporters before the trial today, as he clutched a picture of his son.

The trial is taking place at a district court in Nagoya, 170 miles (270 kilometers) west of Tokyo. At the time of his death, Saito was preparing for the Nagoya Grand Sumo Tournament.

The closed, conservative world of sumo has been hit with numerous scandals recently, including the expulsion of several Russian wrestlers for marijuana use and public accusations of match fixing.