4 bankers have been accused of helping Putin launder $50 million through Switzerland via his cello-playing best friend

• A cellist is accused of helping Vladimir Putin channel $50 million into Swiss accounts.
• 4 bankers are also accused of not having checked the real source of the money.

Four bankers have been accused of helping Vladimir Putin's cellist best friend channel millions of dollars through Swiss bank accounts for the Russian president.

Sergey Roldugin, a concert cellist, is accused by prosecutors of making deposits totalling $50 million with the help of four bankers, who were working as executives in the Russian Gazprombank's Swiss offices, Reuters reported.

The deposits were made between 2014 and 2016 and there is no plausible explanation about where they came from, Swiss prosecutors say.

The bankers, three Russians and one Swiss, appeared in court in Zurich Wednesday accused of lacking diligence in financial transactions, Reuters reported. The four cannot be identified because of Swiss court reporting restrictions.

They have pleaded not guilty, and a verdict is expected by March 30.

Roldugin is a friend of Putin and a godfather of the Russian president's children. He has told The New York Times he is a musician, and not a businessman or millionaire.

The Russian president has an official salary of around $100,000, but his real wealth has long been rumored to be much greater.

"It is notorious that Russian President Putin officially has an income of just over SFr100,000 [$106,000] and is not wealthy, but in fact has enormous assets managed by people close to him," says the indictment by Swiss prosecutors.

In addition to the $50 million, Roldugin was planning on chanelling another $10 million annually into accounts, which prosecutors say "were in general no way plausible as Roldugin's own assets."

The Swiss investigation was sparked by the 2017 Panama Papers leak, which said that Roldugin was channeling millions through networks of offshore accounts into Swiss banks.

Both Putin and Rodulgin were sanctioned by the European Union after Russia's unprovoked invasion of Ukraine last year.

Switzerland has put aside its traditional neutrality in conflicts to adopt the EU's sanctions against Putin, Roldugin, and other members of the Russian elite.