Japan is filled with tension, rather than sadness, on Tuesday as a rare state funeral for the assassinated former Prime Minister Shinzo Abe, one of the most divisive leader, deeply splits the nation.

Tokyo was under maximum security, with a large number of uniformed police mobilize around the Budokan hall, where the funeral is being held, and major train stations. Roads around the venue are closed throughout the day, and coin lockers at main stations were sealed for security.

Hours before the ceremony began, dozens of people carrying bouquets of flowers queued at public flower-laying stands at nearby Kudanzaka park.

Opponents of the state-sponsored honour were to hold rallies elsewhere in Tokyo and around the country. They say tax money should be spent on more meaningful causes, such as to address widening economic disparities caused by Abe's policies.

Prime Minister Fumio Kishida has been criticized for forcing the costly event for Abe, who was assassinated in July, amid widening controversy about him and the governing party's decades-long cozy relations with the ultra-conservative Unification Church, accused of raking in huge donations by brainwashing adherents.

Kishida says the longest-serving leader in Japan's modern political history deserves the honour.

The government says the funeral is not meant to force anyone to honor Abe. But most of the nation's 47 prefectural governments are to fly the flag at half-staff and observe a moment of silence.

Opponents say Kishida's one-sided decision without parliamentary approval was undemocratic, a reminder of how the prewar imperialist government used state funerals to fan nationalism. The prewar funeral law was abolished after World War II. The only postwar state funeral for a political leader, for Shigeru Yoshida in 1967, also faced criticism for lacking legal bases.

"Spending our valuable tax money on the state funeral with no legal basis is an act that tramples on the constitution," rally organizer Takakage Fujita said at Monday's indoor rally.

About 1.7 billion yen (USD 11.8 million) is needed for the venue, security, transportation and accommodation for the guests, the government said.

In a perceived defense for attacks on the funeral, Kishida launched marathon talks with visiting foreign leaders in what he calls "funeral diplomacy" to strengthen ties as Japan faces regional and global challenges, including threats from China, Russia and North Korea. He was to meet about 40 foreign leaders through Wednesday. No Group of Seven leaders are attending.

Kishida met about 10 of them Monday, including US Vice President Kamala Harris, Vietnamese President Nguyen Xuan Phuc and Philippine Vice President Sara Duterte. He will meet with his Australian and Indian counterparts separately and host a reception Tuesday.

About 4,300 people, including Japanese lawmakers and foreign and local dignitaries, are attending the funeral.

Japanese troops will line the streets around the venue, and 20 of them will perform guards of honour outside of Abe's home as his family leaves, then there will be a 19-volley salute.

The ceremony will start when Abe's widow Akie Abe enters the hall carrying a urn containing the ashes of Abe, placed in a wooden box and wrapped in white cloth. The former leader was cremated after a private funeral at a Tokyo temple days after his death.

?Government, parliamentary and judicial representatives, including Kishida, will make condolence speeches, followed by Akie Abe.

?The main opposition Constitutional Democratic Party of Japan and the Japanese Communist Party are boycotting the funeral, along with others.

?Abe's opponents recall his attempts to whitewash Japan's wartime atrocities, his push for more military spending, his reactionary view of gender roles and a leadership seen as autocratic and supportive of cronyism.

Protests of the funeral have increased as more details emerged about Abe's and LDP lawmakers' connection to the Unification Church. The South Korea-based church has built close ties with LDP lawmakers over shared interests in conservative causes.

"The fact that the close ties between the LDP and the Unification Church may have interfered with policymaking processes is seen by Japanese people as a greater threat to democracy than Abe's assassination," wrote Hosei University political science professor Jiro Yamaguchi said in his recent article.

A group of lawyers filed a number of lawsuits at courts around the country to stop the funeral, though one of them was reportedly dismissed Monday. An elderly man had set himself on fire near the prime minister's office in an apparent protest of the funeral.

The suspect in Abe's assassination reportedly targeted him because of Abe's and his party's ties to the church, which he said ruined his life.

Abe's grandfather, former Prime Minister Nobusuke Kishi, helped the church take root in Japan and is now seen as a key figure in the scandal. Opponents say holding a state funeral for Abe is equivalent to an endorsement of party ties to the Unification Church.?