TOKYO (THE YOMIURI SHIMBUN/ASIA NEWS NETWORK) - The suspect in the fatal shooting of former prime minister Shinzo Abe sent a letter hinting that he would kill Mr Abe to a blogger who had been critical of the religious group widely known as the Unification Church.

Tetsuya Yamagami, 41, sent the letter from Okayama City to the blogger who lives in the Chugoku region.

The letter expresses Yamagami's strong resentment towards the group officially called the Family Federation for World Peace and Unification, of which Yamagami's mother is a member, and states that Mr Abe "is not his original enemy".

The Nara prefectural police are aware of the letter and intend to investigate how his resentment towards the group was directed towards Mr Abe.

The former prime minister was speaking in Okayama on the evening of July 7, the day before he was killed in Nara. Yamagami visited the venue of Mr Abe's speech but did not attack him then.

The time of the postmark on the letter indicates that the letter may have been posted on his way to the venue.

The letter was printed on a sheet of A4 paper. It did not give the sender's name but the envelope also contained a copy of an agreement reached when the religious group returned ¥50 million (S$505,094), a portion of his mother's donations, to the Yamagami family.

Yamagami's full name and his address at that time were also written on the agreement.

The man who received the letter from Yamagami runs a blog that criticises the religious group's activities.

Yamagami revealed in the letter that he was a reader of the blog and wrote about his background, saying: "My quarrel against the Unification Church goes back about 30 years."

He added: "I've thought bitterly about him , but he is not my original enemy. Abe is just one of the most influential Unification Church sympathisers in the real world.

"I no longer have time to think about the political meaning and consequences that would result from Abe's death."

Yamagami told investigators that he targeted Mr Abe because he thought the former prime minister was connected with the Family Federation for World Peace and Unification. The police believe he may have been trying to spur criticism of the group by killing Mr Abe.

The man who received the letter operates the blog under his own name and listed his address. He has never met Yamagami, but the letter stated that Yamagami was a reader and had posted in the comments section.

The blogger found the letter in his home mailbox on July 13, five days after the murder. It is believed that the letter was delivered several days earlier.

"What he did is unforgivable," the man told The Yomiuri Shimbun. "I think he probably had no one to talk to and wanted to express his feelings to someone... He may have thought I was his friend because I operate the blog he posted on."

The blogger wrote about the problems experienced by the children of the group's believers.

"I understand the suffering of believers' children," he said. "But I wish he had consulted with me directly before going that far."