Image copyright Reuters Image caption Tsunekazu Takeda shown celebrating in 2013 with the award of the Games to Tokyo

The head of Japan's Olympic Committee is being formally investigated in France for alleged corruption in the awarding of the 2020 Games to Tokyo, a French judicial source has said.

Prosecutors have been investigating a €2m ($2.3m; £1.8m) payment allegedly made by Japan's bidding committee.

Tsunekazu Takeda said he had not been indicted, was co-operating and that there was nothing new in the case.

Tokyo was awarded the Games in 2013, beating Madrid and Istanbul.

The Japanese government has always insisted its Tokyo bid is clean.

The judicial source, quoted by various news agencies and Le Monde, said that Mr Takeda was "mis en examen", or put under investigation, by judges in Paris last month. Mis en examen is the formal start of a criminal investigation under French law.

Speaking to Japanese media, Mr Takeda said this did not amount to indictment, adding "there is nothing new at all, nothing has changed".

He said he had co-operated with a French hearing in December and told it that there had been no improper action.

However, the International Olympic Committee's ethics commission said on Friday it had "opened a file" and would "continue to monitor the situation".

What is the background of the case?

There were few more details given on Friday but the payment concerned appears to be linked to what is known as the Black Tidings case.

French prosecutors said in 2016 they were investigating a payment allegedly made by the Japanese bidding committee to a Singapore-based consultancy firm of that name.

The money was labelled as "Tokyo 2020 Olympic Games Bid", coming from an account opened at a Japanese bank, for the profit of Black Tidings.

Media playback is unsupported on your device Media caption Rupert Wingfield-Hayes reports on the reaction in Japan after Tokyo was awarded the 2020 Olympics

The company is linked to the son of former world athletics chief, Lamine Diack, a member of the IOC when it awarded the Games to Tokyo and who is the subject of a number of corruption allegations.

The son, Papa Massata Diack, also faces corruption allegations. In an earlier interview he told the BBC he and his father were innocent.

In September 2016, an independent panel appointed by Japan's Olympic Committee (JOC) cleared Japanese bidding officials of any illegal activity in the case, saying that the payment to Black Tidings was a legitimate one for consulting services.

Mr Takeda is a veteran Olympics official who competed as a show jumper in 1972 and 1976.

He has been JOC president since 2001.