TOKYO -- Japan's Prime Minister Fumio Kishida said Wednesday his ruling party will cut ties with the Unification Church following a widening scandal triggered by former leader Shinzo Abe's assassination last month, and apologized for causing the loss of public trust in politics.

Widespread cozy ties between members of Kishida's governing Liberal Democratic Party, many of them belonging to Abe's faction, and the South Korean-born church have surfaced since Abe was shot to death while giving a campaign speech in July.

The suspect, Tetsuya Yamagani, who was arrested at the scene, allegedly told police he killed Abe because of his apparent link to the church. In a letter seen by The Associated Press and social media posts believed to be his, Yamagani said he believed his mother's large donations to the church had ruined his life.

Some Japanese have expressed understanding, even sympathy, as details of the man's life emerged, creating deep implications for the political party that has governed Japan virtually uninterrupted since the Second World War.

While religious groups must abide by law, "politicians are strictly required to be careful about groups with social problems," Kishida said. Members of his Cabinet and other key posts have agreed to review their past links and cut ties with the church.

"As president of the LDP, I honestly express my apology" for causing the public's doubts and concerns over the continuing revelations in media reports about the party's extensive ties to the church, Kishida said.

The Unification Church, which was founded in South Korea in 1954 and came to Japan a decade later, has built close ties with a host of conservative lawmakers over their shared interests of opposing communism. Abe's grandfather and former Prime Minister Nobusuke Kishi was a key figure who helped found the church's political unit in Tokyo in 1968.

Since the 1980s, the church has faced accusations of problematic recruiting, sales of religious items and donations, which often lead to financial strains on the followers' families and, according to experts, mental health of adherents' children. The issues has led to the governing party's decision to cut ties with the church.

Abe sent a video message last year to the Universal Peace Federation, an international group affiliated with the church, which experts say may have motivated the suspect in Abe's shooting. Abe had praised the federation's co-founder Hak Ja Han Moon, who is also head of the church, for her effort in promoting traditional family values.

Experts and cult watchers also say that the church has promoted its key agendas such as the opposition to women's advancement and same-sex marriage to influence policy.

Kishida shuffled his Cabinet earlier in August to purge seven ministers linked to the church. Among them was Abe's younger brother Nobuo Kishi, who acknowledged that church followers volunteered in his election campaign. Dozens of LDP members have since come forward with their ties to the church and related organizations.

Kishida said at the news conference that he has instructed LDP Secretary General Toshimitsu Motegi to survey the party fully over any other members' ties to the church. Kishida said he is rushing the effort but it has taken time because the review will span decades.

Kishida apologized for the loss of public trust because of the scandal and his lack of explanation for organizing a state funeral for Abe, one of most divisive leaders in Japan's postwar history.

The state funeral scheduled for Sept. 27 has split public opinion. The only other state funeral in postwar Japan was for former Prime Minister Shigeru Yoshida, who signed the San Francisco Treaty that restored ties with the Allies and ended the U.S. occupation of Japan.

Kishida's Cabinet last week allocated at least a 250 million yen (US$1.8 million) budget to invite about 6,000 guests for the funeral at the Budokan arena in Tokyo.

Kishida insisted that Abe deserved a state funeral because of his achievement in raising Japan's global profile as its longest-serving postwar leader. He said Japan must respond with courtesy to "outpouring of condolences" from foreign leaders and legislations.

Hundreds of people gathered outside the parliament area later Wednesday to protest plans for the state funeral. Holding signs and banners with messages "No to state funeral," "Don't force us to mourn," and "Abe politics destroys Japan," the participants chanted slogans and raised their arms.

The protesters said they refuse to have their tax money spent on condolences for Abe.

"I was so shocked how deeply the Unification Church has been involved in Japanese politics. This is very dangerous," said Yosuke Inai, a retiree who joined the rally.

Chie Sakuma, an office worker, said that if the government had money to spend on the funeral, they should "spend it on something else," noting widening poverty that includes children.

Severing ties with the church "is a serious decision for the party," Motegi said earlier Wednesday, warning of a possible membership expulsion for those who fail to follow the rule. Results of the party review are expected Friday, when the names of those who have accepted donations or help in election campaigns from the church or related groups will be disclosed.

Kenta Izumi of the main opposition Constitutional Democratic Party of Japan criticized the governing party's probe as lax because it does not cover LDP lawmakers in local assemblies, where they are said to have even closer church ties.

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Associated Press video journalist Chisato Tanaka contributed to this report