TOKYO - Japanese Prime Minister Fumio Kishida plans to replace Chief Cabinet Secretary Hirokazu Matsuno amid media reports he received undeclared political funds, the Yomiuri newspaper said on Saturday, citing government and ruling party sources.

Kishida and his ruling Liberal Democratic Party (LDP) are facing mounting scrutiny after allegations party lawmakers, including Matsuno and other high-profile members, may have pocketed more than 100 million yen ($693,000) of fundraising proceeds that were left off the books.

Media have reported that Tokyo prosecutors are looking to investigate lawmakers after the current session of parliament ends on Wednesday.

Kyodo news agency said on Saturday a plan to reshuffle the cabinet and appoint new party officials had also emerged. The changes could happen after the end of the parliament session, it said.

The Asahi newspaper and other media said Matsuno is suspected of having failed to declare more than 10 million yen he received in the past five years from the biggest faction in the LDP. Matsuno has declined to comment on the allegations.

No one was immediately available at Matsuno's office or the prime minister's office to comment on the latest reports.

Industry Minister Yasutoshi Nishimura and Koichi Hagiuda, chairman of the LDP's policy research council, are among those suspected of having failed to declare political funds properly, according to Japanese media.

Nishimura has declined to comment and no one at his office was available to comment on Saturday.

Hagiuda told reporters last week that his organisation has handled the matter in accordance with the law, Kyodo reported. No one was available at Hagiuda's office on Saturday.

Public support for the Kishida's government has slid to a record low partly due to voter worries over rising costs and looming tax hikes.

($1 = 144.18 yen)

(Reporting by Kaori Kaneko, Additional reporting by Yuka Obayashi, Editing by Rosalba O'Brien and Stephen Coates)