The mayor of Nagasaki was shot dead yesterday in an attack which police said was due to an organised crime chief apparently enraged that his car was damaged at a public works construction site.
The shooting was rare in a country where handguns are banned.
Mayor Iccho Ito, 61, was shot twice in the back at point-blank range outside a train station yesterday evening. He died of his wounds after emergency surgery.
Tetsuya Shiroo, a senior member of Yamaguchi-gumi, Japan's largest organised crime syndicate, was wrestled to the ground by officers after the attack and arrested for attempted murder, police said. He later admitted shooting the mayor with a handgun with the intent to kill, Nagasaki chief investigator Kazuki Umebayashi said at a news conference.
Mr Shiroo reportedly clashed with city officials in 2003 after his car was damaged when he drove into a hole at a public works site. He tried unsuccessfully to get compensation from the city after his insurance company refused to pay up, according to Japanese broadcaster NHK.
Backed by the ruling Liberal Democratic Party, Mr Ito was campaigning for his fourth term before Sunday's elections. He was an active figure in the movement against nuclear proliferation, heading a coalition of Japanese cities calling for the elimination of nuclear weapons.
Japan's organised crime groups, known as Yakuza, have a long-standing political alliance with right-wing nationalists, although authorities did not indicate that the attack was politically motivated.