Japan on Friday said it would question officials involved in Tokyo's successful 2020 Olympics bid over a multi-million dollar payment which is being probed by French investigators.

Japan's announcement comes after French prosecutors said they suspect that $2 million paid to a son of disgraced former world athletics supremo Lamine Diack was aimed at winning support for the Tokyo 2020 bid.

‘We will further work to confirm facts,’ top Japanese government spokesman Yoshihide Suga told a regular press conference, citing the French probe.

The allegation follows earlier controversies surrounding the Tokyo Olympics, which had to scrap its original main stadium design due to its hefty pricetag, and had to weather plagiarism accusations over the Games' logo.

Olympic Minister Toshiaki Endo said the government's Sports Agency will speak to officials from the Tokyo metropolitan government and the Japanese Olympic Committee.

However, Suga and Endo both said they were confident that no wrongdoing occurred, based on previous declarations by officials.

‘I don't believe that such (corruption) took place,’ Endo told reporters, adding that he will be closely watching the outcome of the Japanese probe.

Suga said the government had already received a report that the bid committee did not make such a payment after suspicions first emerged in January following a report by the World Anti-Doping Agency.

While Japanese officials strongly deny any wrongdoing by the Tokyo bid, the Asahi Shimbun daily quoted ‘several bid committee members’ as saying there was a team outside the formal bid committee that conducted ‘unknown’ activities.

- 'No such payments' -

Some 2.8 million Singapore dollars (1.8 million euros, $2 million) paid to a company owned by Papa Missata Diack is at the centre of the suspicions, French prosecutors said in a statement Thursday.

Diack father and son already face corruption charges in France.

Two payments were made in 2013 to Black Tidings, a Singapore-based company linked to Papa Diack, who was employed by the International Association of Athletics Federations (IAAF) as a consultant, the prosecutors said.

The International Olympic Committee chose Tokyo over Istanbul and Madrid as host for the 2020 Games in September 2013. Diack senior was an IOC member at the time.

Suga on Thursday insisted that the bid was ‘clean’, and other officials reiterated that stance on Friday.

‘All money is accounted for’ in the Tokyo bid team's records and no such alleged payments were made, a Tokyo metropolitan government official in charge of the 2020 Games told AFP.

The alleged payments were discovered as part of an inquiry into allegations that the Diacks organised bribes to cover up failed dope tests by Russian athletes, French prosecutors said. France became involved as the money may have been laundered in Paris.

Prosecutors said the money was ‘labelled as 'Tokyo 2020 Olympic Games Bid', coming from an account opened at a Japanese bank, for the profit of the 'Black Tidings' company in Singapore’.

After growing public opposition, Tokyo replaced its original, $2 billion stadium design with a cheaper design last year.

Last month, organisers unveiled a new Tokyo 2020 logo after claims that an earlier version closely resembled the emblem of a theatre in the Belgian city of Liege.