Candidates for Japan's ruling Liberal Democratic Party's (LDP) presidential election take part in a debate at the Japan National Press Club in Tokyo on September 14, 2024. (AP)

Japan's parliament will formally elect a new prime minister on October 1, after next week's leadership contest, a ruling party official announced on Wednesday.

Polls are showing three frontrunners are emerging among the nine candidates contending to succeed Fumio Kishida as leader of the Liberal Democratic Party (LDP) in the upcoming internal vote on September 27.

The three candidates are conservative Economic Security Minister Sanae Takaichi, the LDP's former Secretary-General Shigeru Ishiba, and Shinjiro Koizumi, son of former prime minister Junichiro Koizumi.

Koizumi would be the country's youngest prime minister while Takaichi, who serves as a prominent nationalist with the LDP's conservative wing, would be Japan's first woman premier.

However, Takaichi's candidacy is likely to provoke victims of the country's wartime aggression, including China, the DPRK, and South Korea, since she is a frequent visitor to the Yasukuni shrine, which honors Japan's war dead, including convicted war criminals.

LDP seeks victory in upcoming election

Japan's conservative LDP has ruled the country for decades, holding the majority seats in parliament, suggesting the winner of the party election is likely to become premier.

The LDP "plans to convene a parliament session on October 1" to elect the new prime minister, the party's lawmaker Yasukazu Hamada informed the opposition, a LDP official told AFP.

The opposition party accepted the date, which the government will formally announce on Monday, according to media reports.

Kishida announced his resignation last month after facing scandals, voter anger over inflation, and sliding poll ratings, ending his three-year rule.

Each of the LDP's 367 members will cast their votes in the upcoming leadership election, while an additional 367 votes will be determined by the preferences of rank-and-file party members and supporters.

Japan's leading PM candidate Koizumi promises snap election

On September 6, Japan's former environment minister and leading prime ministerial candidate Shinjiro Koizumi said he would call for a snap election "at the earliest date possible" if he were to win the ruling party's leadership election this month.

Koizumi pledged to "essentially continue" the economic policies of the current Prime Minister Fumio Kishida's administration if he were to become the next prime minister.

During a news conference announcing his intention to run in the race, Koizumi said, "I'll aim to beef up the underlying strength of the Japanese economy so that growth can be attained even in an era where inflation and higher interest rates coexist."

He stated that if he became prime minister, his priority would be to introduce a new economic package to support small businesses and low-income households affected by rising living costs.