Japanese Prime Minister Fumio Kishida was evacuated from a port in Wakayama after a blast was heard, but he was unharmed in the incident, local media reported Saturday.
Several reports, including by Kyodo news agency, said an apparent “smoke bomb” had been thrown but there were no immediate signs of injuries or damage at the scene.
A person was detained at the site in western Japan’s Wakayama where Kishida had been due to give a speech, national broadcaster NHK and others said.
There was no immediate official confirmation of the incident, with local police declining to comment.
NHK showed footage of security and police detaining an individual as a crowd scattered at the scene.
Japan has bolstered security after the assassination of former prime minister Shinzo Abe, who was shot and killed while speaking at a campaign event in July 2022.
The incident comes as Japan hosts G7 ministerial events in northern Sapporo and the city of Karuizawa in Nagano, and ahead of the May leaders’ summit in Hiroshima.