Japanese Prime Minister Kishida Fumio was uninjured after a man threw what appears to have been a bomb at the site of a campaign speech in western Japan on Saturday.
Kishida left the site after the explosion and has been confirmed safe. Authorities say one police officer suffered minor injuries.
Kishida was visiting Saikazaki Port in Wakayama Prefecture on Saturday morning to offer support to his party's candidate in a by-election planned later this month. His speech at the fishing port was cancelled.
Police arrested 24-year-old Kimura Ryuji who lives in Kawanishi city in Hyogo prefecture. He is under arrest for suspicion of forcible obstruction of business. The suspect has reportedly remained silent.
Investigative source told NHK the suspect had two cylindrical objects, one of which exploded. The other was seized by authorities.
Kishida later went ahead with a planned speech in front of JR Wakayama Station.
Kishida said: "We are holding an important election across the country and we have to work together to see it through to the end."
Kishida's next speech was delivered in Chiba prefecture. This round of local elections will take place on April 23, when voters choose mayors and assembly members in smaller municipalities. By-elections to fill vacancies in five lower and upper house seats will also be held on April 23.
Investigative sources say the cylindrical object believed to have exploded at the site of Prime Minister Kishida's planned speech is likely made of metal. They say the explosion shattered the tube.
Police say they seized two objects at the scene. Eyewitness reports suggest a light on one object illuminated prior to its explosion. Police suspect it may be what is known as an "iron pipe bomb."
This type of explosive is made by sealing each end of a pipe packed with gunpowder and fitted with a detonator. Such a bomb will explode when air pressure inside the pipe reaches a certain level after the gunpowder ignites.
Police believe the suspect was in possession of the remaining bomb when he was apprehended. They say there was no explosion, and plan to analyze the mechanism in detail.
Former Prime Minister Abe Shinzo was shot and killed in the city of Nara last July. He was giving a speech during an election campaign. Yamagami Tetsuya, 42-year-old, was indicted on a number of charges, including murder.