TOKYO — Japanese police arrested a man Thursday on suspicion of threatening to kill top sumo wrestler Asashoryu.

The Tokyo Metropolitan Police said Chiharu Takahashi, 29, allegedly posted a death threat on the popular Japanese Internet forum 2channel from his home computer on Sunday, the opening day of the New Year Grand Sumo Tournament.

The threat said "Coming to Ryogoku to kill Asashoryu," a police spokesman said on condition of anonymity, citing department policy. Ryogoku Kokugikan in Tokyo is Japan's main sumo venue. The threat prompted police to tighten security at the venue.

Mongolian Asashoryu was unaware of the threat at the time, defeating his opponent Sunday. The 28-year-old popular sumo champion remained unbeaten in the tournament with 5-0 record Thursday.

The suspect was quoted as telling investigators that he had been disgusted with Asashoryu's behavior as a grand champion and posted the message for fun, according to Kyodo News agency. The police spokesman declined to confirm the report.

Asashoryu, the subject of recent retirement speculation, has reached the rank of yokozuna, the highest in the sport.

He had previously been the first yokozuna ever suspended, when it was revealed he participated in a football game in Mongolia despite citing injury to skip tournaments. Asashoryu had also been criticized for not living up to the behavioral standards of a sumo champion in a sport associated closely with Japanese traditional culture.