Agents searched a Moscow bank Friday that is controlled by billionaire tycoon Alexander Lebedev, his aide said.

Former KGB spy Lebedev was not at the National Reserve Bank when several agents from the Federal Security Service arrived for the search, Artyom Artyomov said.

The FSB agents did not appear to be armed and were not wearing masks, Artyomov said. He added that Lebedev was also concerned by checks by about 130 officials from the Central Bank.

"We do not know what the FSB search is about. You will have to ask them yourself," Artyomov said. "The officials from the Central Bank are interested in the personal accounts of Alexander Lebedev, including the accounts he uses to finance his newspapers."

A spokesman for the Federal Security Service said he had no information about the search and declined further comment.

Lebedev has ruffled feathers in the Kremlin in recent years by funding an opposition newspaper and poking fun at Prime Minister Vladimir Putin, who he says must open up the political system or face turmoil in coming years.

Lebedev's bank was raided in 2010 by armed police in masks, and he has complained in interviews of being under attack by corrupt officials in the law enforcement agencies.

Lebedev, who served in Russian foreign intelligence under diplomatic cover in London, made his billions trading stocks and bonds after the 1991 collapse of the Soviet Union.