Japan's sumo authority decided Wednesday to cut the pay of two grand champions who failed to stop a brutal assault by a fellow champion on a junior wrestler.

The Japan Sumo Association announced that grand champions (yokozuna) Hakuho and Kakuryu would not receive a salary in January, while Hakuho would forfeit half his pay in February.

The two Mongolians failed to restrain their compatriot Harumafuji, also a yokozuna.

Harumafuji reportedly flew into a rage last October during a drinking session after a tournament, when a lower-ranked Mongolian wrestler tried to use his phone while Hakuho was speaking to him.

Harumafuji retired last month to take responsibility for the incident, which left the junior wrestler with a fractured skull.

Police and prosecutors are investigating the case.

Association chair Hakkaku said Hakuho and Kakuryu must also accept responsibility because they "failed to prevent the violence that was being carried out in front of them by a fellow yokozuna".

Harumafuji's stable-master Isegahama has stepped down from the sumo authority's board, he said.

Hakuho is the most successful yokozuna in history with 40 tournament victories.