The sacked chief executive of Japan's disgraced Olympus Corp says he has accepted an invitation to attend its board meeting this week, in what could be a hopeful sign for investors who want him to return and lead a clean-up of the firm.

Olympus, a maker of cameras and medical equipment, has been engulfed by an accounting scandal and is under investigation by regulators, prosecutors and also organised-crime police. The scandal broke when CEO-turned-whistleblower Michael Woodford publicly questioned its accounts after being fired last month.

I was invited to the board meeting on Friday by Olympus and welcome the opportunity of going to Japan, Woodford, a Briton, told Reuters in London on the eve of his departure for Tokyo, his first trip back to Olympus headquarters since his sacking at a board meeting just over five weeks ago.

Woodford has been cast by two major foreign shareholders as the best man to lead a clean-up of the 92-year-old company, which has lost about 65 percent of its market value since he first went public with his concerns of improper accounting.

Olympus, which initially flatly denied any wrongdoing, has since admitted to hiding investment losses from investors for two decades and to using some of $1.3 billion (831 million pounds) in unusual merger and acquisition payments to help in the cover-up.

It was not immediately clear whether the man who presided over Woodford's sacking, former chairman and president Tsuyoshi Kikukawa, would also attend the board meeting. Kikukawa quit as chairman over the scandal last month but remains a director.

Speculation of organised-crime links have swirled around the Olympus scandal, but the firm said on Monday that a third-party panel it set up to investigate the matter had, so far, found no evidence that funds from its M&A deals went to organised crime syndicates or that yakuza gangsters were involved.

The panel's report is due in early December.

Woodford has cited unspecified security concerns for his decision to leave Japan in a hurry after he was sacked, but said on Monday he was now comfortable about returning and reiterated his willingness to go back and run the company.

I'm reassured about the security. The Japanese authorities are aware and arrangements have been made that I'm satisfied with, the 31-year Olympus veteran said.

Woodford, who remains a director despite his sacking as an executive, would not discuss the agenda of the board meeting, saying only that it would be an opportunity to ask my colleagues to do the best for Olympus.

Woodford has said he would meet Japanese police and other authorities during his visit this week.

SPECULATION OVER ORGANISED CRIME

The scandal at the once-proud firm has rekindled concerns about lax corporate governance in Japan and revived worries about links between companies and organised crime.

A unit from the Tokyo Metropolitan Police Department's organised crime division has joined the investigation, a source familiar with the matter said on Friday. But the source added it was premature to say if gangsters were involved.

Olympus shares, however, jumped as much as 20 percent in early trade on Tuesday on speculation the company might avoid being delisted from the Tokyo Stock Exchange, despite the scandal. The stock last traded up 16 percent at 840 yen.

Speculators who believe Olympus' core medical equipment business still has value have been betting that executives responsible for the scandal will bear the brunt of any punishment and that the company can escape with a fine.

Olympus has admitted to improperly accounting for M&A payments going back to 2006. A large share of these payments went to obscure Cayman Islands companies that have since closed, making it difficult to trace the money.

Tokyo prosecutors have already questioned former vice-president Hisashi Mori on a voluntary basis, Japanese media say, and are expected to soon question ex-president Kikukawa and internal auditor Hideo Yamada over their roles in the scandal.

Olympus' new president, Shuichi Takayama, has blamed the three for the cover-up, saying he would consider criminal complaints against them. Mori was sacked as an executive this month but, like Kikukawa, remains a director. It is also unclear whether Mori will attend this week's board meeting.

The Tokyo exchange has placed Olympus on a watch-list as a possible prelude to delisting. If the firm misses a December 14 deadline for filing its financial statements for the six months to September, it will be automatically delisted.

Even if Olympus meets the deadline, the bourse can still delist the stock depending on the scale of its past financial misstatements or if the firm is found to have done business with organised crime syndicates.

(Additional reporting by Kirstin Ridley in London and Lisa Twaronite in Tokyo; Editing by Linda Sieg and Mark Bendeich)