TOKYO — A Japanese court convicted three sumo wrestlers Thursday for their part in the death of a younger stablemate during training last year, a case that has damaged the image of the country's ancient national sport.

Junior wrestler Tokitaizan, a 17-year-old whose real name is Takashi Saito, died in June 2007 after collapsing following practice. An autopsy showed bruises and injuries on his body that indicated assaults rather than ordinary sumo training.

The Nagoya District Court sentenced 25-year-old Yuichiro Izuka and 26-year-old Masakazu Kimura to three years in prison, and 23-year-old Masanori Fujii to two and half years in prison, all suspended for five years, court spokesman Shunichi Ito said. The three wrestlers won't be jailed unless they commit another crime while on probation.

The wrestlers beat Saito on the head with bear bottles and repeatedly slapped him on the face the night before his death, the court said. During training the next day, they repeatedly threw him to the ground, hit him with a baseball bat and showered him with water from a hose.

The young wrestler collapsed a short time later.

Trainer Junichi Yamamoto is also charged with assault resulting in death. He's set to stand a separate trial at a date yet to be set, Ito said.

The 58-year-old Yamamoto, who was later fired by the Japan Sumo Association, has denied any part in Saito's death.

Judge Masaharu Ashizawa acknowledged Thursday that the three convicted wrestlers had to unconditionally obey instructions from their trainer, public broadcaster NHK said. The judge also noted that violent punishment was considered standard practice at sumo stables.

"I take the ruling very seriously," trainer Tokitsukaze said in a televised interview. "I'm committed to properly oversee the stable so we'll never repeat the mistake."

The world of sumo has been rocked by a spate of recent scandals, including the expulsion of several Russian wrestlers for marijuana use and allegations of match fixing.

In the rigid, traditional world of sumo, a stable takes care of training and welfare for young recruits — only a fraction of whom become professional fighters. Many drop out due to the rigorous training and harsh living conditions.

Saito's father said his son had fled the stable twice, including the day before his death, but returned each time. Saito was training for a tournament in Nagoya in central Japan at the time of his death.