TOKYO — Former Nissan and Renault boss Carlos Ghosn was controversially rearrested in Japan on Thursday, just a month after being released on bail and a week before he planned to hold a news conference to present his side of the story.

Japanese prosecutors said the latest arrest was based on suspicion he diverted $5 million to a company he controlled, from funds that were being relayed from a Nissan subsidiary to an overseas dealership.

Ghosn had tweeted Wednesday that he would hold a news conference April 11 to “tell the truth” about the case. But his situation soon took a dramatic turn for the worse when Renault accused him of “questionable and concealed practices and violations of the group’s ethical principles,” and Japanese prosecutors moved swiftly to place him back in detention.

Ghosn called the arrest “outrageous and arbitrary.” His attorneys protested that it was unnecessary — since he had surrendered his passport, was not a flight risk and was under strict bail conditions to prevent evidence tampering. They also said it was unfair because the prosecutors confiscated his phone as well as documents relating to his defense.

“Why arrest me except to try to break me?” Ghosn said in a statement. “I will not be broken. I am innocent of the groundless charges and accusations against me.”

In a news conference, Ghosn attorney Junichiro Hironaka called the arrest “outrageous.”

“For them to arrest him without rationale or necessity is, I must say, a violent act,” he said, protesting the confiscation of documents necessary for Ghosn’s defense and trial. “This goes against the intention of the law. They should not have done this as a civilized country.”

Hironaka also complained that prosecutors seized the phone and passport of Ghosn’s wife, who was with him at the time of his arrest. “His wife is not a suspect,” he said. “This is unforgivable.”

But as questions continue to mount about the treatment Ghosn is receiving at the hands of Japanese prosecutors — treatment that many legal experts consider to be unfair — his conduct at the head of the Nissan-Renault alliance is also coming under greater scrutiny.

The French carmaker said Wednesday that its internal investigation, including a probe of payments made to a dealership in Oman, has shown a serious lack of transparency in the management of its alliance with Japan’s Nissan Motors. Renault said it would halt Ghosn’s pension and reserved the right to bring action against him in the courts.

That marked the first time Renault had publicly turned against its former star executive. Until now, the investigation and charges had been driven by Nissan and Japanese prosecutors.

In a statement, Ghosn’s representatives described the new Japanese charges as “legally dubious” and said they came after he had been detained for 108 days in “extremely unfair, cruel and unjust conditions.” Ghosn called the arrest “part of another attempt by some individuals at Nissan to silence me by misleading the prosecutors.”

Ghosn was initially arrested in November and subsequently rearrested twice more while still behind bars, a common tactic used by Japanese prosecutors to prolong detentions. He was accused of breach of trust and financial misconduct before being released on $9 million bail under strict conditions last month.

The case has thrown an unflattering spotlight on Japan’s justice system and the considerable power of prosecutors to prolong detentions almost indefinitely to extract confessions, a system often labeled “hostage justice.”

Nobuo Gohara, a former prosecutor who runs his own law firm and has been sharply critical of the handling of the case, said the latest arrest reflected prosecutors’ concerns that the existing charges may not have been sufficient for a guilty verdict.

“This is beyond hostage justice,” he said. “It looks as though prosecutors are doing their utmost to destroy Ghosn’s defense team.”

Jacques Deguest, an angel investor based in Tokyo, said the treatment of Ghosn has had a negative impact on the perception of Japan among fund managers and business executives investing or working in the country. This is raising investment risks and even making some people scared to continue working here, he said. Prosecutors are widely seen as applying a “double standard” to Ghosn and Japanese business leaders, Deguest said. 

“The law has to be reliable and predictable,” he said. “These are two pillars of the economy for any country in the world.”

Gohara said the law allows prosecutors to confiscate evidence relating to the new charges. But he said that taking away documents at a time when the preparations for Ghosn’s defense would have been at their most intense was neither fair nor a sensible application of the law, and made it seem that prosecutors were trying to obstruct the defense.

Ghosn initially was accused of underreporting his income to the tune of tens of millions of dollars, although he said the payments were to be made in the future and never had been formally agreed upon. He also was accused of temporarily transferring personal losses to Nissan’s books in the wake of the financial crisis; he says Nissan never lost any money over the arrangement.

Many commentators have linked the case against Ghosn to resentment within Nissan’s Japanese senior management of his attempts to forge an even closer alliance between the French and Japanese carmakers. 

But even if that resentment lay behind the initial charges, Ghosn’s defense appears to have been complicated by the fact that Renault has turned against him.