Prosecutors on Monday demanded a 15-year prison term for a man accused of attempted murder after a pipe bomb attack two years ago that targeted an election event attended by then Prime Minister Fumio Kishida.

Ryuji Kimura, 25, is accused of hurling an explosive device at Kishida, who was walking near a crowd gathered for a stump speech in the western Japan city of Wakayama in April 2023. The incident came less than a year after the assassination of former Prime Minister Shinzo Abe.

"The explosives were lethal and there was intent to kill. It was a malicious act of terrorism targeting the sitting prime minister and involving many others," a prosecutor said at the Wakayama District Court.

Prosecutors based their claims on an analysis by police and forensic scientists that found the device had the power to propel shrapnel in a way that would penetrate a 9-millimeter plywood board, fast enough to break a human skull.

The bomb was thrown into a crowd of more than 100 people and the explosion could have killed anyone, prosecutors said.

"Targeting the incumbent prime minister could have had an enormous impact on national politics. It shook the very foundation of democracy and affected subsequent election campaigns," the prosecutor said.

Kimura denied his intent to kill, saying during the trial that he was dissatisfied with the electoral system and was just trying to bring attention from the public by creating a disturbance at an event attended by a famous politician.

His defense team argued that he should not face a charge of attempted murder, as he did not expect the bomb to cause injuries.

Meanwhile, Kimura pleaded guilty Monday to a charge of disrupting an election under the public offices election law, admitting he knew Kishida was visiting for an election-related event. He had earlier denied the charge by arguing he was unaware there was a by-election being held.

According to the indictment, Kimura traveled to a fishing port in Wakayama on April 15, 2023, where Kishida was preparing to make a speech ahead of a House of Representatives by-election.

The homemade pipe bomb explosion caused minor injuries to a police officer and a member of the public. Kishida was unhurt.

The verdict will be handed down on Feb 19.