Hiroto Saikawa is suspected of improperly adding $440,000 to his compensation by altering bonus terms

The CEO of crisis-hit Japanese auto giant Nissan plans to resign, local media reported on Monday, days after admitting he received more pay than his entitlement.

The reports said it was not immediately clear when Hiroto Saikawa would step down, as the firm struggles with the aftermath of the arrest of its former chief Carlos Ghosn on charges of financial misconduct.

Nissan said it had no immediate comment on the reports, which first emerged overnight in the Nikkei business daily.

Nikkei said Saikawa has told several Nissan executives of his intent, but that no date for his resignation nor a successor has been decided.

The reported decision comes days after Saikawa acknowledged that a Nissan probe revealed he had received more pay than he was entitled to, in a scheme under which directors can receive a bonus if their company's share price rises above a certain level in a set period.

Saikawa is suspected of improperly adding 47 million yen ($440,000) to his compensation by altering the terms of a bonus, according to reports.

Nissan has not confirmed the details of the payments, but Saikawa apologised last week, while denying any wrongdoing.

"I left the issue to someone else so I had thought it was dealt with in an appropriate manner," he told reporters.

Nissan is due to hold a board meeting later Monday, where details of the investigation that revealed the overpayments are expected to be shared.

The car maker is currently undergoing an overhaul intended to strengthen governance after the Ghosn scandal.

In June, Nissan shareholders voted in favour of various measures including the establishment of three new oversight committees responsible for the appointment of senior officials, pay issues and auditing.

They also approved the election of 11 directors as the firm restructures, among them two Renault executives as well as Saikawa.

The reforms are designed to put Nissan on a more stable footing after the arrest of Ghosn, who has been sacked from his leadership roles at the Japanese firm and others.

He is awaiting trial on charges of under-reporting millions of dollars in salary and of using company funds for personal expenses.

Ghosn has denied any wrongdoing and accuses Nissan executives opposed to his plans to further integrate the firm with France's Renault of plotting against him.