Several top ministers in Japanese Prime Minister Fumio Kishida's cabinet are set to be fired reportedly over an investigation for alleged fraud, according to reports Monday.

Those to be axed, potentially as early as this week, include Kishida's right-hand man Chief Cabinet Secretary Hirokazu Matsuno and Yasutoshi Nishimura, the minister of economy, industry and trade, the reports said.

According to Japan's influential daily, Asahi Shimbun, the total number to be sacked will be 15, including several deputy ministers and parliamentary vice ministers.

All belong to a faction formerly headed by late Prime Minister Shinzo Abe – one of at least five major groupings vying for influence and power within the ruling Liberal Democratic Party (LDP).

Prosecutors are investigating allegations that the faction failed to report tens of thousands of dollars raised through fundraising parties, according to recent media reports.

Another of those reportedly implicated is former Olympic minister Seiko Hashimoto.

On Monday Kishida refused to be drawn on the possible reshuffle – which could take place once the current session of parliament ends on Wednesday – but said he took the fraud allegations seriously.

"I'm thinking of taking appropriate measures at an appropriate timing for the sake of recovery of the public's trust (in the government), and for preventing delays in government operations," Kishida told reporters.

Kishida's poll ratings are at their lowest levels since he took office two years ago, in part because of voter unease over inflation.

The latest survey published on Monday by Fuji TV and the Sankei Shimbun daily put public support for his cabinet at 22.5%, down from 27.8% last month, while the disapproval rating is at 71.9%, up from 68.8%.

This is despite a previous reshuffle in September and a stimulus package worth 17 trillion yen ($117 billion) announced in November for the world's third-largest economy.

Kishida, 66, can govern until 2025 but there has been speculation that he might call a snap election ahead of a likely tough internal leadership vote in the LDP next year.

The opposition was set to file a non-confidence motion against the Kishida cabinet to the parliament on Tuesday, although it was unlikely to pass.

The Constitutional Democratic Party of Japan, the largest opposition, also submitted a no-confidence motion against Matsuno on Monday.

The lower house is expected to take up the motion against Matsuno on Tuesday.