In this Sept 16, 2020 file photo, Japan's outgoing Prime Minister Shinzo Abe speaks to the media upon his arrival at his office in Tokyo. (KAZUHIRO NOGI / AFP)

TOKYO - Hotel documents show former Japanese prime minister Shinzo Abe's camp paid part of the expenses for a dinner party held for his supporters the night before an annual cherry blossom viewing party, NHK public TV said on Monday, citing unnamed sources.

Politicians in Japan are strictly forbidden to give anything to constituents that could be construed as a gift. The rule is so strict that one cabinet minister quit in 2014 after distributing paper fans during the summer

Politicians in Japan are strictly forbidden to give anything to constituents that could be construed as a gift. The rule is so strict that one cabinet minister quit in 2014 after distributing paper fans during the summer.

In May, about 660 lawyers and scholars filed a complaint with Tokyo prosecutors seeking an investigation into whether Abe and two executives of his political support group broke campaign and funding laws by subsidizing the attendance of backers at the reception in 2018, Kyodo news agency then reported.

Abe has denied any wrongdoing.

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NHK said Tokyo prosecutors had questioned one of Abe's aides and some others on a voluntary basis as part of their investigation.

Reuters' calls to Abe's offices in Tokyo and in his constituency of Shimonoseki in western Japan went unanswered on Monday, a public holiday in Japan.

But Kyodo news agency said Abe's office issued a statement saying that it was cooperating with the prosecutors' investigation.

No one was immediately available for comment at the Tokyo District Public Prosecutors Office or at the Hotel New Otani, where the reception was held in 2018.

Attendees each paid a 5,000 yen (US$48) admission fee for the annual party, but opposition lawmakers said the admission price was much lower than that of other receptions held at the upscale hotel.

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Abe, Japan's longest-serving prime minister, stepped down in September due to health problems, but has stayed on as a lower house lawmaker.