Russian prosecutors opened a criminal case against Berezovsky, 60, who has been living in London since 2000 and was granted political asylum in 2003, after he told a radio station that he was planning to overthrow the administration of President Vladimir Putin.
"The investigation will continue as it has been extended until December 16," said Andrei Borovkov, who represents Berezovsky's interests.
Another attorney acting for Berezovsky refused to comment on the progress of the investigation in the interests of client confidentiality.
In an interview with Ekho Moskvy radio station on January 24, Berezovsky, who was a prominent player in the Kremlin in the 1990s and helped bring Putin to power before falling out of favor, said the president had violated the constitution and any violent action on the opposition's part was justified. "That includes taking power by force, which is exactly what I am working on," he said.
Hopes for securing Berezovsky's extradition increased and prosecutors filed another extradition request after British authorities condemned his statements. Jack Straw, then Britain's foreign secretary, criticized Berezovsky's comments in a statement February 23.
"I am aware of the comments made by Mr. Boris Berezovsky in an interview on January 24," Straw said. "Advocating the violent overthrow of a sovereign state is unacceptable, and I condemn these comments unreservedly." Straw also warned Berezovsky that the U.K. government could review his political refugee status.
Russian prosecutors previously demanded Berezovsky's extradition in 2002, when a warrant for his arrest was issued on charges of fraud regarding carmaker AvtoVAZ. The prosecution also declared Berezovsky the main suspect in the embezzlement of large sums from Aeroflot, Russia's national air carrier, in which he owned a significant stake. However, the British authorities turned down Russia's extradition request and Berezovsky dismissed the charges as politically motivated.
The exiled tycoon made his fortune in the turbulent 1990s in dubious privatization deals following the collapse of the Soviet Union. His financial assets helped him rise to power and become a Kremlin insider under ex-President Boris Yeltsin.
