The company said its investigation found that Ghosn, 64, and the other board member, Greg Kelly, had been under-reporting Ghosn's compensation.
Saikawa said he couldn't elaborate as the cases are being investigated by prosecutors, who have declined to comment.
After Renault sealed an alliance with Nissan in 1999, Ghosn used similar methods to revive the ailing Japanese brand, leading to "business superstar" status in Japan, blanket media coverage and even a manga comic book on his life.
Spokesmen for Renault and the Renault-Nissan-Mitsubishi Motors alliance did not immediately return calls and messages seeking comment on the arrest reports. "Looking back, after 2005 when he became CEO [chief executive] of both Renault and Nissan, we did not really discuss the implications", he said.
The extent of the misconduct allegations, or the arrest charges, were unclear as of Monday morning.
Nissan's Saikawa said Ghosn's alleged improprieties came to light through a whistleblower, after which the company began an internal investigation and informed prosecutors.
Ghosn had been criticized for his salary of about $9 million ー exorbitant by Japanese standards.
As auto markets in western Europe and Japan struggled, Ghosn championed a cheap car for the masses in emerging markets and embraced the electric vehicle before many others.
Nissan and Mitsubishi have already said they will propose removing Carlos Ghosn as chairman.
It said Nissan's chief executive, Hiroto Saikawa, will recommend to the board that Ghosn is removed from his role as chairman.
Hamas leader signals interest in Gaza truce
Israel responded with more than 100 airstrikes on Gaza, including one that leveled the studios of the Hamas-affiliated al-Aqsa TV. A Palestinian labourer from the occupied West Bank was killed when a rocket hit a building in the Israeli city of Ashkelon.
Nissan said it also planned to oust senior executive Greg Kelly, who had been "deeply involved" in the misconduct.
Speaking on the sidelines of a eurozone finance ministers' meeting in Brussels, French Finance Minister Bruno Le Maire said the government would "do everything as a shareholder represented on Renault's board to ensure operational continuity and stable governance at Renault".
Carlos Ghosn has been accused of breaching Japanese financial trading law. He told reporters that the investigation had identified "serious misconduct". The arrest comes after Nissan revealed that an internal investigation concluded that the long-time executive allegedly under-reported his income and misused corporate assets.
Ghosn added Mitsubishi to the alliance two years ago after the tiny automaker was caught in a gas-mileage cheating scandal.
The Washington Post reported that Ghosn was arrested Monday.
The French state owns 15 per cent of Renault, which in turn holds a 43.4 per cent stake in Nissan.
He is credited with saving Nissan from bankruptcy through measures including closing plants and restructuring, and he has instant name recognition in Japan, where he is a rare high-profile foreign executive.
On Monday, Japanese prosecutors said Mr Ghosn had under-reported his income from running Nissan by 5bn yen ($44.4m; £34.5m) over five years.
Mr Ghosn joined Nissan in 1999 after Renault bought a controlling stake and became its CEO in 2001, remaining in that post until past year.