Russian billionaire senator Suleyman Kerimov was charged Wednesday with tax fraud in Nice, hours after Moscow protested his arrest in the French Riviera resort.

Kerimov was detained upon arrival at the airport on Monday, where he faced two days of questioning over alleged tax evasion involving the purchase of luxury properties.

He has now been released under strict conditions including handing over his passport and posting bail of five million euros. He also faces restrictions on his movement, state prosecutor Jean-Michel Pretre said. 

A source close to the probe told AFP that Kerimov was accused of hiding tens of millions of euros from tax authorities while buying a string of properties on the glitzy Riviera through intermediaries.