Japanese authorities have found the man accused of killing former prime minister Shinzo Abe fit for trial after a lengthy psychiatric assessment, local media said Tuesday.

Television footage showed Tetsuya Yamagami being transferred to a police station in western Nara from a detention centre in neighbouring Osaka, where he had spent the past five months while undergoing the assessment.

The evaluation found the 42-year-old to be fit for prosecution, according to the Yomiuri Shimbun newspaper.

Prosecutors are set to indict him by Friday, national broadcaster NHK said.

Local police and prosecutors declined to comment on Yamagami's case when reached by AFP.

Yamagami was apprehended at the scene after Abe was shot to death in broad daylight as he gave a campaign speech in Nara in July.

The suspect reportedly targeted Abe in the belief that the former premier was linked to the Unification Church.

Yamagami is reported to have resented the church over large donations his mother made that left his family bankrupt.

His psychiatric review focused on his relationship with his mother and home environment, local media said.

Abe, who was given a rare state funeral, was not a member of the church but had addressed an affiliated group, as have other powerful speakers such as former US president Donald Trump.

Founded in Korea in 1954 by Sun Myung Moon, the church -- whose members are sometimes referred to as "Moonies" -- rose to global prominence in the 1970s and 80s.

The church, officially known as the Family Federation for World Peace and Unification, has denied wrongdoing and has pledged to prevent "excessive" donations from members.

Abe's killing prompted unexpected revelations of close ties between the church and many conservative, ruling lawmakers, angering the public and causing approval ratings for Prime Minister Fumio Kishida's administration to plummet.

Kishida has ordered a government investigation that could see the Unification Church lose its tax-exempt status in Japan, although it could still continue to operate.