Japanese Prime Minister Fumio Kishida was unhurt after a smoke bomb was thrown at him before he was set to make a speech in Wakayama prefecture, according to national broadcaster NHK.
A man was taken into custody at the venue, Kyodo reported citing the police. Kishida was evacuated from the scene to Wakayama police headquarters, Kyodo said.
Kishida had been touring a fishing port in Wakayama, which is in central Japan near Osaka, and was set to give a speech, the reports said.
Video posted online by Japanese news outlets showed multiple police tackling a figure at the port, while a crowd scattered around them.
Japan has been on high alert over security for its politicians after former Prime Minister Shinzo Abe was shot and killed last June. The island nation is about to host the G-7 summit for world leaders in Hiroshima next month, and security had been a high priority considering the Abe shooting.