TOKYO (REUTERS, AFP) - Ousted Nissan boss Carlos Ghosn promised to "tell the truth" at a news conference next week, taking to Twitter to announce his first briefing since being released on bail and hours after a report that prosecutors were preparing a fresh case against him.

Ghosn, widely lauded for rescuing Nissan Motor Co from the brink of bankruptcy two decades ago, has experienced a dramatic fall from grace that shook the global auto industry and raised questions about the future of Nissan's alliance with France's Renault SA.

He was arrested in Tokyo in November and faces charges of financial misconduct and aggravated breach of trust over allegedly failing to report around US$82 million (S$111 million) in salary and temporarily transferring personal financial losses onto Nissan's books during the financial crisis.

Released on US$9 million bail last month, Ghosn has denied the charges, calling them "meritless" and saying he was the victim of a boardroom coup.

"I'm getting ready to tell the truth about what's happening. Press conference on Thursday, April 11," Ghosn tweeted from the #carlosghosn account on Twitter, which displayed the blue tick mark indicating it had been verified by the social media site.

It was the sole tweet, posted in Japanese and English, on the account, which was created this month.

A spokesman, when contacted by Agence France-Presse, confirmed that the Twitter account was authentic and that Ghosn would speak at a press conference on April 11.

Under the terms of Ghosn's bail, he is not allowed to use the Internet, although the tweet may have been made on his behalf, as is common with celebrities and other high-profile figures.

Earlier, Japan's Yomiuri newspaper reported that Tokyo prosecutors are preparing to build a fresh case against him over suspect payments the automaker made to a business partner in Oman.

Prosecutors are in discussions with the Supreme Public Prosecutors Office and others and plan to make a decision soon on whether to prosecute Ghosn on further charges of aggravated breach of trust, the newspaper said, citing sources involved in the case.

Ghosn's spokesman has previously said payments of US$32 million made over nine years were rewards for the Oman firm being a top Nissan dealer. Such dealer incentives were not directed by Ghosn and the funds were not used to pay any personal debt, the spokesman said.

Sources told Reuters earlier this week that Renault SA had alerted French prosecutors after uncovering suspect payments to a Renault-Nissan business partner in Oman while Ghosn was chief executive of the French automaker.

Nissan had previously established that its own regional subsidiary had made questionable payments of more than US$30 million to the Oman distributor, Suhail Bahwan Automobiles (SBA).

Evidence sent to French prosecutors late last week showed that much of the cash was subsequently channelled to a Lebanese company controlled by Ghosn associates, the sources said.

Reuters has not been able to reach SBA for comment on the matter.