Japan's ruling party said on Tuesday it will select a new leader - and by extension the likely next prime minister - on Sep 27.

The decision follows current Prime Minister Fumio Kishida's announcement last week that he will not seek re-election, after polls showed plummeting approval ratings for his government.

Campaigning to become the next Liberal Democratic Party (LDP) president will begin on Sep 12 with a vote two weeks later, an internal committee decided early Tuesday, a party official told AFP.

Kishida's exit announcement on Aug 14 means that his tenure as prime minister will end in September after just under three years.

The 67-year-old has seen his poll ratings, along with the LDP, slide sharply in response to rising prices hitting Japanese incomes and several scandals.