TOKYO, - Scandal-hit Olympus is suing 20-odd current and former executives for damages over a massive investment loss cover up at the Japanese firm, reports said Monday.

The law suits filed in Tokyo on Sunday named ex-president Tsuyoshi Kikukawa, pegged as playing a major role in the embarrassing affair, and his successor Shuichi Takayama, the Yomiuri Shimbun said, citing sources close the case.

Earlier reports said Takayama will step down this month after an in-house panel probing the cover up named him among those responsible for the scandal.

The embattled camera and medical equipment maker's former vice president Hisashi Mori and former auditor Hideo Yamada were also believed to be among those sued, the Nikkei business daily said on Monday without citing sources.

The combined damage claims could total hundreds of millions of dollars against more than 10 Olympus officers, the Nikkei said on Sunday before the company announced it was considering lodging law suits.

Earlier reports have said the damages claim could top $1.0 billion. Olympus officials were not immediately available to comment on Monday, which was a public holiday in Japan.

The Sunday statement came after an in-house panel investigated the responsibility of Olympus board members in a scandal that rocked the 92-year-old firm and undermined public trust in Japanese corporate governance.

"Upon receiving the report (on Saturday), we are currently discussing filing law suits against the current and former board members," it said.

Olympus said it would disclose the report's findings and discuss the company's future plans on Tuesday.

The three-lawyer panel was tasked with investigating the exact responsibility of the Olympus board members in the scandal.

A separate committee of former judges and outside experts, commissioned by the company, condemned Olympus' top management as "rotten."

The company has admitted that a small group of top executives hid at least 134.9 billion yen (S$2.2714 billion) in losses from bad investments in the 1990s.

Japanese authorities have launched a criminal investigation into Olympus, raiding its headquarters in Tokyo last month and questioning its former executives in the alleged fraud.

The scandal came to light after its first foreign president Michael Woodford exposed the matter last year by talking to the international media and authorities, as Olympus' old guard quickly sacked him from the top post.

Despite months of campaigning to overhaul the Olympus board, Woodford has given up his efforts to return to and lead the company due to lack of support from major Japanese institutional shareholders.

Olympus avoided having its shares automatically pulled from the Tokyo Stock Exchange when it filed its delayed earnings report on a December 14 deadline, revealing a 32.3 billion yen loss in the first half of the year.

The exchange could still delist its shares, but would likely allow Olympus stock to remain on the bourse because its liabilities, including the hidden losses, never exceeded its assets, the Nikkei said on its website Monday.

But the bourse may designate Olympus stock as one of its securities on alert, the report said, meaning the company would have to file annual progress reports on efforts to improve corporate governance and information disclosure.

A delisting would remain possible if sufficient progress was not made within three years.

Shares in the camera-maker closed 2.13 per cent higher at 1,053 yen on Friday, less than half their value the day before Woodford was forced out.