One of Russia's best-known businessmen, Vladimir Gusinsky, has been arrested in Greece on Russian multi-million-dollar fraud charges.
Gusinsky was a key figure in Russia during the Yeltsin years
Mr Gusinsky was detained on Saturday after flying in from Israel where he had been living in self-imposed exile, and will face an Athens appeals court on Monday.
Greece has confirmed he was arrested under a treaty with Russia after initial reports suggested he had been detained under an Interpol search warrant.
A lawyer for the businessman has reportedly challenged the legality of the arrest.
Since his fall from political grace in Russia under President Vladimir Putin, the former owner of the prestigious NTV television channel and other media has been living abroad.
The Greek authorities said Russia was seeking to prosecute him over alleged fraud worth $250 million.
Greek Government spokesman Christos Protopapas said Mr Gusinsky had been detained "on an arrest warrant issued by Russia and a Greek-Russian agreement on co-operation in judicial matters".
In July 2001, Interpol's Secretary General, Ronald Noble, opposed issuing a warrant against Mr Gusinsky, saying that Russia's case against him had "a predominant political character".
Reuters news agency quoted Athens police sources as saying that a lawyer for the detainee was arguing that the warrant against him was invalid.
Mr Gusinsky is scheduled to appear before the prosecutor of the Athens court of appeal on Monday, said Mr Protopapas.
Fall from grace
The former media magnate moved to Israel from Spain in April 2001 after a Spanish court refused to extradite him to Moscow on an earlier fraud warrant.
MAKING OF A MOGUL
Born in 1952, Vladimir Gusinsky studied at Moscow Institute of Petrol and Gas, then at
Worked as a theatre director and, at one stage, a private taxi-driver before going into business
Founded Most Bank in 1989, went on to launch NTV and Segodnya newspaper
Together with fellow tycoon Boris Berezovsky, Mr Gusinsky enjoyed great power and influence under the presidency of Boris Yeltsin but rapidly fell out of favour when Mr Putin came to power in late 1999.
His media outlets, which were renowned for freely reporting sensitive stories such as the wars in Chechnya and administrative corruption, were also quickly taken over by pro-Kremlin interests.
Police arrested him at Athens airport after he arrived on a flight from Tel Aviv.
No details have been given as to why Mr Gusinsky, who also holds an Israeli passport, was travelling to Greece.
The BBC's Russian affairs analyst, Stephen Dalziel, reports that Mr Gusinsky's fate will be closely watched by fellow Russian businessmen.
These include Mr Berezovsky who is currently in Britain battling a Russian request for his extradition on similar charges.
The case will be also be of interest, our analyst adds, to another of the so-called Russian oligarchs, Roman Abramovich, who is the new owner of Britain's Chelsea football club.
Mr Abramovich, recognised as the wealthiest among this informal group, has recently come under Kremlin pressure.