The suspect, who appeared to have thrown the pipe-like bomb at a port in Wakayama where Kishida was visiting, has been arrested, national broadcaster NHK reported, citing police sources.
NHK footage shows crowds of people running away as smoke filled the area where a loud explosion was heard, and police officers pressing the suspect to the ground.
The object, resembling a flare with smoke, was thrown at Kishida at around 11:30 a.m. local time while he was preparing to deliver an outdoor speech supporting the by-election of the House of Representatives, according to Kyodo News and other media outlet.
Local media reports said he immediately took cover and left the scene after the incident, adding there were no injuries or damage.
Kishida, currently at the Wakayama Prefecture main police headquarters, canceled his public speech in the area, Kyodo News reported.
The incident occurred as Japan is hosting Group of Seven (G7) ministerial meetings in northern Sapporo and the city of Karuizawa in Nagano ahead of the G7 leaders’ summit in Hiroshima next month.