Geneva's chief prosecutor said on Monday he had closed a criminal investigation into allegations Spain's former king Juan Carlos laundered "illegal commission" payments from Saudi Arabia, due to insufficient evidence.

A Swiss private bank involved in the three-year criminal probe was convicted of a reporting failure and fined.

Prosecutor Yves Bertossa said he had established that Saudi Arabia had paid $100 million in August 2008 into an account opened a month before at Mirabaud private bank in the name of a Panamanian foundation whose beneficial owner was Juan Carlos.

But Bertossa said in a statement that he had been unable to prove a sufficient link with a contract awarded three years later to Spanish companies for a high-speed rail connection in Saudi Arabia.

The Spanish royal household declined to comment on the development. Juan Carlos, who is living in exile in the United Arab Emirates, could not immediately be reached for comment.

Through his lawyer, Juan Carlos has previously declined to comment on the various allegations of wrongdoing against him. The former king's Geneva asset manager was quoted in court documents as testifying that a Saudi ambassador had described the funds as a "pure gift".

Bertossa said he had opened the criminal investigation in 2018, following news reports that the former king, who abdicated in 2014, may have received "illegal commissions" linked to the contracts and stashed the funds in Swiss accounts.

"The investigation has established that Juan Carlos I did, in fact, receive $100 million on the Lucum foundation account at Mirabaud & Cie SA in Geneva, from the Saudi finance ministry on Aug. 8, 2008," Bertossa said.

The use of a foundation and offshore accounts by various protagonists in the case had showed a "willingness to dissimulate", but he had been unable to sufficiently prove the relation between the Saudi payment and the contract for the rail link between Medina and Mecca, he said.

CHARGES DISMISSED

Additional payments of nearly $9 million from Kuwait and Bahrain were received on accounts held by Juan Carlos and his German-born former lover, Corinna Zu Sayn-Wittgenstein, Bertossa said. She received the balance of 65 million euros ($73.3 million) from the Mirabaud account, which was closed in June 2012 and the funds transferred to her account in Bahamas, the prosecutor added.

Charges handed down against four accused, whom court documents show included the asset manager, a lawyer and a banker, as well as Zu Sayn-Wittgenstein, for alleged "aggravated money-laundering" were dismissed, Bertossa said. Juan Carlos was not among the five indicted suspects, which also included the bank ,charged with failure to report an account's unusual activity under the money-laundering law.

"Today I have finally been cleared of wrongdoing of any kind in the three-year investigation conducted by the Swiss prosecutor," Zu Sayn-Wittgenstein said in a statement sent to Reuters.

"My innocence was evident at the outset and this episode has served to harm me further as part of the ongoing abuse campaign against me by certain Spanish interests."

"The principal wrongdoers, meanwhile, have not been investigated and have been given time to conceal their activities. They remain unaccountable," she said.

Mirabaud bank was fined 50,000 Swiss francs ($54,100) for having failed to report Zu Sayn-Wittgenstein's account and its unusual activity of funds received from the foundation owned by the former king, the prosecutor's statement said.

The bank said in a statement it welcomed the closure of the criminal proceedings. It said its alleged violation of a duty to report did not concern the account linked to the former Spanish king and it had developed and strengthened its internal procedures since.