A court in south-western Japan has sentenced the head of a powerful crime syndicate to death by hanging.

The court in the city of Fukuoka found that Nomura Satoru, aged 74, had ordered four assaults, one of which resulted in death.

The verdict came despite a lack of direct evidence against Nomura, local media said. He denied any involvement.

It is believed to be the first time a senior member of Japan's mafia, the yakuza, has been sentenced to death.

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"I asked for a fair decision… You will regret this for the rest of your life," Nomura told the presiding judge after his sentencing on Tuesday, according to Japan's Nishinippon Shimbun newspaper.

Nomura, who heads the Kudo-kai syndicate operating in south-western Japan, plans to appeal.

Although prosecutors had no direct evidence Nomura had ordered violent attacks, they successfully argued that his absolute command over the group meant he had ultimate responsibility.

During the four assaults between 1998 and 2014, a former boss of a fishing co-operative was killed, and three other people, including a police officer, were injured.

Sentencing Nomura on Tuesday, the judge described his actions as extremely vicious.

Yakuza groups are not illegal in Japan, and they frequently operate front companies out of smart offices.

Analysts say the gangs are involved in every area of criminal activity in the country, from drug-running and prostitution to stock-market manipulation.