A seven-figure payment from the successful Tokyo Olympic bid team to a notorious account linked to the son of the disgraced former world athletics chief Lamine Diack was apparently made during the race to host the 2020 Games.

The Guardian has learned the alleged payment of around €1.3 million, now believed to be under scrutiny by French police, will increase pressure on the International Olympic Committee (IOC) to investigate properly links between Diack’s regime and the bidding race for its flagship event. It could also raise serious questions over Tokyo’s winning bid, awarded in 2013

Any suggestion that votes could have been bought will be hugely embarrassing for the IOC, which has set great store by the probity of its bidding process since wholesale reforms following the Salt Lake City bribery scandal which erupted before the winter Games of 2002.

Diack Sr was an IOC member between 1999 and 2013, becoming an honorary member in 2014 before resigning in November last year after allegations he had accepted more than €1 million in bribes to cover up positive Russian doping tests. He is now prevented from leaving France while prosecutors there investigate corruption at athletics’ governing body.

In March, the Guardian revealed that the French investigation had widened to include the bidding races for the 2016 and 2020 Olympics.

It is now understood that among transactions under suspicion are payments totalling around €1.3 million apparently sent from the Tokyo 2020 bid, or those acting on their behalf, directly to the Black Tidings bank account in Singapore. The account is linked to Papa Massata Diack, the son of Lamine Diack who was employed by the International Association of Athletics Federations (IAAF) as a marketing consultant.

Lamine Diack, the longstanding former IAAF president, was still an influential IOC member in 2013 when Tokyo triumphed over fellow bidders Istanbul and Madrid.

The secret Black Tidings account is at the heart of the allegations of institutionalised corruption at the IAAF over more than a decade.

An independent report commissioned by the World Anti-Doping Association (Wada) and published in January showed how Diack and his sons, Papa Massata and Khalil, who were employed as marketing consultants, joined up with the lawyer Habib Cisse to function “as an informal illegitimate governance structure” of the IAAF.

The Guardian had earlier revealed that Papa Massata Diack, who had carte blanche to seek sponsorship deals in developing markets under an agreement with marketing partner Dentsu, appeared to request $5 million (€4.4 million) from Qatar at a time when it was bidding for the 2017 world athletics championships and the 2020 Olympics.

In January, the Guardian also revealed that Papa Massata Diack was in 2008 apparently involved in a scheme to deliver “parcels” to six influential members of the IOC at a time when the Qatari capital Doha was attempting to bid for the 2016 Olympics.

But the latest revelations are perhaps the most troubling yet for the IOC and will send shockwaves through the Olympic movement at a time when president Thomas Bach has repeatedly held it up as an example of probity to other troubled sporting organisations including Fifa and the IAAF.

Asked about the alleged payment, believed to have been made in more than one tranche before and after the Games were secured, the Japanese Olympic Committee – which oversaw the bid – said its press team was away on business for a week and was unable to respond.

The Tokyo 2020 organising committee said it had no knowledge of what went on during the bid period. The spokeswoman Hikariko Ono said: “The Tokyo 2020 Organising Committee has no means of knowing these allegations. We believe that the Games were awarded to Tokyo because the city presented the best bid.”

The allegations come at a difficult time for the IOC, which is under pressure over this summer’s Rio de Janeiro Olympics amid a host of practical and political issues and locked in an ongoing battle to persuade potential bidding cities that the Games remain a worthwhile prize.

The seven-figure payment from Tokyo 2020 could also raise new questions about the role of Dentsu, the Japanese marketing giant that has an all-encompassing sponsorship contract with the IAAF that runs until 2029 having been unilaterally extended by Diack in the final months of his presidency.

The report by Wada’s Independent Commission, chaired by Dick Pound, explained in detail how the Black Tidings account was held by Ian Tan Tong Han, who was a consultant to Athlete Management and Services, a Dentsu Sport subsidiary based in Lucerne that was set up to market and deliver the commercial rights granted to it by the IAAF.

Computer analysis revealed that Tan had regular high-level access to IAAF officials including Lamine Diack and was “integrated into the IAAF at the executive level” and “appeared to be part of the informal governance system for the IAAF”.

Tan’s relationship with Papa Massata Diack was so close that he named his child, born in 2014, Massata. The report said that Tan appeared to have ongoing business interests related to the Diack family in Singapore and Senegal. Papa Massata Diack remains in Senegal, despite an Interpol notice having been issued for his arrest.

In response to questions from the Guardian, a Dentsu spokesman said it had no knowledge of any payment to Black Tidings and that Tan was never employed as a consultant. One of the world’s largest marketing companies, it has previously said that Papa Massata Diack was not employed as a consultant by Dentsu and that his contract was with the IAAF.

The Black Tidings account first came to prominence when it was revealed that it was the channel for a €300,000 refund paid to the Russian marathon runner Liliya Shobukhova in March 2014 following a botched attempt to cover up a positive drugs test.

The IAAF’s independent ethics commission began investigating the affair later that year and in a damning 170-page report in January banned four senior officials, including Papa Massata Diack and its former anti-doping chief Gabriel Dolle, over the corruption and extortion racket. The Pound report points out that Black Tidings in Hindi means Black Marketing or, literally, to “Launder Black Money”.

Sources have told the Guardian they believe “tens of millions” of euros passed through the account. Two separate, independent sources with knowledge of the investigation have confirmed the seven-figure payment from the Tokyo 2020 bid is being investigated.

Possible wrongdoing in the 2020 race was referred to in a footnote to Pound’s report that suggested Diack dropped his support for Istanbul and switched to Tokyo because a Japanese sponsor signed a deal with the IAAF.

At the time, Tokyo 2020 said the claims were “beyond our understanding” and Istanbul’s bid said it did not believe it was a factor in their defeat. The IOC said it would examine a transcript of the conversation on which the claims were based.

Papa Massata Diack, who is believed to be in Senegal despite an Interpol red notice issued against him, met police for seven hours earlier this year. However, the authorities have said he will not be deported. “These allegations are currently under investigation by the French police and in the Court of Justice. I do not wish to make any comment as I am also part of this legal process,” he told the Guardian.

The IOC, which will gather in Rio for its 129th session before the summer Games, said its chief ethics and compliance officer had been in contact with the French magistrates investigating the IAAF case, and with Wada since its inception, and that the IOC was now a civil party to the French justice procedure.

A spokesman addded: “The IOC’s chief ethics and compliance officer will continue to be in contact with all interested parties to clarify any alleged improper conduct. The IOC will not comment any further on the elements of the investigations at this stage.”

(Guardian service)