PARIS - Police, some of them armed, swooped down by helicopter to the luxury French Riviera villa of self-exiled Russian tycoon Boris Berezovsky, seizing documents and computers in a daylong search, police said Thursday.

Berezovsky was not at the rented seaside villa on the Cap d'Antibes when the raid took place Wednesday -- in fact, he hasn't been there for four years, he said -- but his 81-year-old mother was.

"Initially she thought it was a performance of the Cannes Festival ... because people were armed and in masks," he told The Associated Press by telephone. The film festival in nearby Cannes opened Wednesday.

French police "came by helicopter with many armed people" and spent 10 hours at the villa, he said in an account confirmed by police.

About a dozen officers, some armed and several wearing plain clothes, took part in the search, said a police official in Cannes, who asked not to be named. He said the raid was part of an investigation, but provided no details about who ordered the probe or why.

Berezovsky said he did not know what prompted the raid, but had nothing to fear.

"I know what I'm doing. I know how I build business and I'm sure that everything that I build is absolutely legal," he said.

Berezovsky, a fierce political opponent of Russian President Vladimir Putin, got rich in the chaotic period of 1990s post-Soviet capitalism. He has been charged with embezzling funds from Aeroflot, Russia's national airline. He has rejected the charges as politically motivated.

Berezovsky lives in Britain, where he was granted political asylum in 2003.