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Switzerland's banks are well known for their secrecy in handling clients' financial affairs. (Reuters)

Four bankers have been charged with moving millions of francs through Swiss bank accounts for Russian President Vladimir Putin.

The four bankers, three Russians and one Swiss, allegedly helped Putin's friend Sergey Roldugin deposit millions of francs in Swiss bank accounts on Putin's behalf, Swiss prosecutors said during the trial held on Wednesday.

The trial was held at Zurich District Court in connection with the case that focuses on two bank accounts opened in the name of Roldugin. The bankers have been accused of helping him move millions without due diligence checks.

Swiss prosecutors told the court that the bankers failed to identify the true beneficial owner of the funds, thereby, helping Putin's friend hide millions for him. The two bank accounts were opened in 2014, but Roldugin did not have enough evidence to show the source of his funds.

"All the evidence runs contrary to Sergei Roldugin being the real owner of the assets," the prosecutor, Jan Hoffmann, told the court.

"The bankers have not followed the rules and should therefore be punished," he added. They have sought suspended sentences of seven months for all four bankers.

"It is well known that...Putin officially only has an income of 100,000 Swiss francs, and is not wealthy, but in fact has enormous assets which are managed by persons close to him," read the indictment.

However, the bankers denied the charges, and the defence lawyer claimed that there was nothing to prove that Roldugin was not the real owner of the funds.

"Doubts about the identity of the true owner are not enough from a criminal law point of view," said the defence lawyer. A decision in the case is to be announced on March 30.

Roldugin, a concert cellist and director of a Moscow musical academy has often been described as "Putin's wallet." He is one of the members of Putin's inner circle who were sanctioned by the West after Russia declared war on Ukraine.

According to a Reuters report, he has no listed business activity. And there is nothing to show for the millions he deposited in the Swiss bank accounts. Putin once claimed that Roldugin is a brilliant musician and earned his money from a minority stake in a Russian company.

He also dismissed reports suggesting that the money Roldugin owned was linked to him. He said that it was anti-Russian "Putinophobia" and that his financial records are in the public domain.

Roldugin's name first cropped up in the Panama Papers leak in 2016. The investigation by the International Consortium of Investigative Journalists revealed that he played a significant role in channelling some $2 billion through numerous offshore companies.

The Panama Papers revealed how the world's rich were using offshore tax havens to hide billions. The investigation revealed the wealth stashed away by 72 current or former heads of state.

Russian President Vladimir Putin, Pakistan's PM Nawaz Sharif, Ukrainian President Petro Poroshenko, the King of Saudi Arabia, and Bashar al-Assad were among the people whose names came up in the investigation.

As many as 11.5 million records of offshore holdings from the secretive Panamanian law firm Mossack Fonseca were obtained by the German newspaper Süddeutsche Zeitung and shared with more than 100 other media. The revelations had taken several governments by storm, but Putin remained unfazed.

Roldugin's brother studied with Putin at the KGB's training academy. In 1985, he became godfather to Putin's daughter Maria.

"We met and then never split. He is like a brother. Back in the day when I had nowhere to go, I went to him and slept and ate at his place," Rodulgin said, in an excerpt from the book carried by the Organized Crime and Corruption Reporting Project (OCCRP).