Il Nuovo Postiglione - Race to become Japan's next PM kicks off

Whoever wins the Liberal Democratic Party (LDP) leadership vote on September 27 will succeed unpopular Prime Minister Fumio Kishida, whose three-year term was tarnished by scandals and unease over rising prices.

The contest comes as Japan beefs up defence spending and cooperation with fellow US allies to counter China and as the world's fourth largest economy struggles with a slow-burn demographic crisis.

The conservative LDP has governed almost uninterrupted for decades and holds a majority in parliament, meaning the winner is essentially guaranteed to become premier.

Leading the polls are Shinjiro Koizumi, 43, a former environment minister and the son of ex-premier Junichiro Koizumi, and veteran former defence minister Shigeru Ishiba, 67.

"I want to change the politics of Japan, left behind by the changing times," Koizumi said as the candidates each made a campaign speech at the LDP headquarters.

His pledges include labour market deregulation, making political funds more transparent, and to "settle issues that have been debated for years" such as allowing married couples to have separate surnames.

Meanwhile Ishiba, highlighting regional tensions, referred to North Korea's ballistic missile test on Thursday morning.

"They are not doing this as a joke," he said, arguing of the need to build an organisation like NATO in East Asia.

- Prominent women -

Also in the running are two prominent women -- still a rarity in Japanese politics and business.

Hard-right Sanae Takaichi, 63, is a regular visitor to the Yasukuni shrine to Japan's war dead -- including those convicted for war crimes committed during Japan's brutal occupation of China and Korea.

Japan's economic security minister, Takaichi promised to "make the LDP a party that the Japanese people can believe in".

And although her support within the party is limited, Foreign Minister Yoko Kamikawa, 71, is seen as a deft leader who aspires to mentor younger female politicians.

Outspoken reformist Taro Kono, 61, is also a candidate, as is Toshimitsu Motegi, dubbed the "Trump whisperer" for his handling of the former US president in tough trade talks.

Others include chief cabinet secretary Yoshimasa Hayashi and former economic security minister Takayuki Kobayashi, the only other candidate under 50 along with Koizumi.

In his emotional speech on Thursday, Koizumi also described meeting his birth mother for the first time this year.

- Snap polls predicted -

Displayed outside its party headquarters on Thursday was a large poster reading "The Match" with black-and-white photos of previous leaders.

Speculation is rife in local media that the winner will call a snap election for as soon as late October or early November.

The main opposition Constitutional Democratic Party is also in the midst of its own leadership contest.

The LDP race is seen as the most open in years, with Kishida having pushed many of the party's powerful factions to disband following a damaging slush fund scandal.

"A healthy degree of policy debate has been taking place as the LDP seeks renewal," said analyst James Brady from consultancy firm Teneo.

"Most candidates are making generous spending promises, while some oppose planned tax hikes," he wrote in a note.

LDP presidents are in office for three years and can serve up to three straight terms.

The opinion polls are only a rough guide, since only LDP lawmakers and regional party representatives have a vote following a series of public debates among the candidates.

M.Dodaro--INP