Bunji Nakamura, the 55-year-old leader of regional crime syndicate Chushinkai, was seriously hurt in a shooting early on Sunday in Kumamoto in southern Japan, local media reports said.

Police were searching for two men who fled the scene, Kyodo news agency and other domestic media said, adding that police suspect the shooting may have been an act of reprisal against the fatal shooting of another gang leader at the weekend.

Kyodo said Chushinkai was part of a group that had broken off from a major regional crime syndicate called Dojinkai, whose 56-year-old boss, Yoshihisa Matsuo, was shot dead in Fukuoka in southern Japan on Saturday.

Public broadcaster NHK reported that local police were stepping up their guard, worried that the conflict between gang groups could escalate. Police in Kumamoto were not immediately available for comment.

Gun-related crimes are relatively rare in Japan, which nonetheless has been rattled by a number of gangster-related shootings this year.

In May, Japanese police nabbed a former gangster after a standoff lasting more than 24 hours during which the man shot a policeman dead after wounding his own son, daughter and another police officer and holing up in his suburban house.

In April, a gangster shot a fellow mobster in a Tokyo suburb and hid in an apartment before shooting himself, and another gangster shot dead the mayor of Nagasaki, shocking a country where gun control is tough.