Police say the 41-year-old suspect said he had believed rumors that Abe was connected to a religious organization that caused his family financial problems.

He also told investigators he had attempted to make a bomb. Meanwhile a handmade gun found at the scene was one of several confiscated from his apartment.

But Abe's death has raised security questions. A top police official has admitted that possible security lapses allowed the assassin to get in close range of the prime minister in broad daylight.

"I believe it is undeniable that there were problems with the guarding and safety measures. The urgent matter is for us to conduct a thorough investigation to clarify what happened," said Tomoaki Onizuka, head of the Nara prefectural police.

The veteran politician has been praised by mourners and leaders for his knowledge and experience in international politics and for preventing the deterioration of US-Japanese relations.

While the assassination has overshadowed Sunday's parliamentary election, the ruling Liberal Democratic Party were predicted to come out top as voters cast their ballots.

Current Japanese Prime Minister Fumio Kishida who leads the conservative party denounced the "barbaric" attack on his former mentor, insisting on the importance of "defending free and fair elections".