Former Tokyo 2020 operations chief Yasuo Mori is one of four further arrests in the latest swoop by Japanese prosecutors investigating bribery ©Getty Images

Japanese prosecutors have made four further arrests in connection with allegations of bid rigging for contracts related to test events in Tokyo before the Olympics.

Tokyo 2020 Operations Executive Yasuo Mori has been arrested and had his home searched by agents investigating the assignment of contracts in violation of the anti-monopoly law.

Mori's arrest was described as "extremely regrettable" by Tokyo Governor Yuriko Koike who has instructed the liquidation corporation for the now dissolved Tokyo 2020 Olympic Organising Committee to continue to cooperate with authorities.

A Japanese Olympic Committee statement said: "We are not aware of the details and will monitor the developments closely."

In the most recent swoop by prosecutors, Dentsu advertising agency executive Koji Hemmi was also detained.

Event production executives Yoshiji Kamata from Cerespo Company and Fuji Creative Corporation’s Masahiko Fujino were also arrested. 

The offices of both companies were also searched by investigators in cooperation with the Japan Fair Trade Commission.

Both had won contracts to plan test events. 

Prosecutors have made further arrests over allegations of bribery in organising test events for the Tokyo 2020 Olympics ©Getty Images
Prosecutors have made further arrests over allegations of bribery in organising test events for the Tokyo 2020 Olympics ©Getty Images

Mori is understood to have collaborated with Dentsu personnel to arrange successful bidders for test events.

Prosecutors have alleged that he exchanged emails with companies to influence the bidding process.

Mori initially denied knowledge of the activities but is said to have admitted his involvement after Dentsu officials revealed they had colluded in fixing contracts.

The offences are thought to have taken place in 2018 when 26 open tenders to organise Tokyo 2020 test events were launched.

These were awarded to nine companies, including Dentsu and fellow ad giant Hakuhodo Inc, for a total of JPY538 million (£3.4 million/$4.1 million/€3.82 million).

The successful companies also received contracts for the Olympic and Paralympic competitions, said to be worth JPY40 billion (£250 million/$305 million/€280 million).

Last August, prosecutors arrested former Tokyo 2020 Executive Board member Haruyuki Takahashi, who now stands accused of receiving around JPY200 million (£1.2 million/$1.4 million/€1.3 million).

In December, the fallout from the scandal prompted the decision to suspend Sapporo's bid for the 2030 Winter Olympics.