Japanese prosecutors have formally indicted a 24-year-old man on attempted murder and other charges over the explosives attack on Prime Minister Fumio Kishida in April, court officials said.

Mr Kishida was campaigning for elections in a small fishing port in Wakayama in western Japan when a man threw a homemade pipe bomb at him.

Mr Kishida was unhurt, but two people received minor injuries.

Suspect Ryuji Kimura, 24, was arrested on the spot and underwent a three-month psychiatric evaluation sought by local prosecutors to determine that he is mentally fit for trial.

Police and prosecutors determined that the bomb used in the attack was potentially lethal, according to local media reports.

Prosecutors indicted Kimura on an attempted murder charge and four others, including violation of the gun and swords control law and the explosives control law, according to the Wakayama District Court, which accepted the indictment.

A trial date has not been decided, court officials said.

In the indictment, prosecutors allege that Kimura threw the pipe bomb at Mr Kishida with an intent to kill and caused minor injuries to a police officer and a local resident in the audience, Kyodo News reported.

Kimura has refused to talk to the authorities.

The attack came about a year after former prime minister Shinzo Abe was fatally shot while campaigning for elections in Nara in western Japan.

Gun and bomb violence in Japan is rare, and the attacks on Mr Abe and Mr Kishida shocked many in the country. The attacks prompted greater police protection of dignitaries and a review of safety measures during election campaigns.