Prime Minister Fumio Kishida's decision to hold the funeral on Sept. 27, to be paid for by the state, has aroused widespread public opposition, largely because of revelations that emerged after Abe's murder of ties between the ruling party and a controversial church group.

"I humbly accept the criticism that my explanation was insufficient," Kishida told members of parliament in response to questions about the issue.

Abe, Japan's longest-serving but divisive premier, was shot and killed at an election rally on July 8.

His suspected assassin, arrested at the scene moments after the killing, bore a grudge against the Unification Church, alleging it bankrupted his mother, and blamed Abe for promoting it.

A majority of the public feels links between the ruling Liberal Democratic Party (LDP) and the church, which was founded in South Korea in the 1950s and is famous for its mass weddings, have not been adequately explained.

Many voters are also sceptical that the political party will cut ties with the church, as Kishida has promised. The LDP is set to announce the results of its investigation into members' links later on Thursday.

Using information available on legislators’ websites and sources including videos posted by the church, Reuters has identified at least 65 LDP lawmakers – including Abe and 23 members of his right-wing faction – who attended church events, sent it messages of congratulation, paid membership fees, accepted political donations from its affiliates or received election help.

Kishida has said he decided to hold a state funeral given Abe's contributions to the country and his achievements, which have been recognized at home and abroad.

'Reasonable'

But criticism of the funeral could increase as the cost has risen to US$12 million, and is likely to rise even more because of expenses such as security for foreign dignities, who are expected to include United States Vice President Kamala Harris, Indian Prime Minister Narendra Modi and Australian Prime Minister Anthony Albanese.  

A representative from Taiwan will also attend, although the self-ruled island is still discussing who will go.  

"Even in comparison to similar ceremonies that were held in the past, we believe the estimate is reasonable," Kishida said in response to a question on whether costs were too high.

A poll this week showed disapproval of Kishida's government had increased to more than 40 percent of those questioned for the first time since he took office last year. Other surveys have shown disapproval edging above approval.

Though Kishida does not have to hold a national election for three years, growing disapproval could make it hard to push through an agenda that includes bringing more nuclear reactors back online.

Political analysts say it may be hard for Kishida to regain much ground with the public in the short term given that the funeral is several weeks away.

"This issue will drag on," said Airo Hino, a political science professor at Waseda University, noting that Kishida may have waited too long to explain his decision.

"As the day of the funeral approaches and disapproval continues to grow, his support is likely to fall still further."