Japan's police chief Itaru Nakamura has announced he will resign over the assassination of former Prime Minister Shinzo Abe.

Nakamura said he wanted to take responsibility for the July 8 shooting.

The investigation revealed that serious mistakes were made in defending the former prime minister.

Abe was shot while speaking at a political campaign event in the city of Nara.

The 41-year-old shooter was able to approach Abe from behind and shoot him with a makeshift pistol as he was making a speech.

According to doctors, the 67-year-old ex-premier received two bullet wounds to the neck and damage to the heart.

Local police have already acknowledged undeniable shortcomings in Abe's security.

Shinzo Abe is Japan's most famous politician.

Security experts who reviewed video footage of the attack previously told Reuters news agency that bodyguards could have saved Abe by covering him or pulling him out of the line of fire within 2.5 seconds between the first missed shot and the fatal second shot.

Suspected Tetsuya Yamagami was arrested at the scene and confessed to shooting Abe.

He admitted that he shot Abe because he thought he was connected to a religious group that Yamagami said bankrupted his mother.