France has joined the US and Russia in seeking the extradition of a Russian held in Greece for allegedly laundering $4 billion using the bitcoin digital currency, a court source said Wednesday.

The French warrant says Alexander Vinnik, who headed bitcoin exchange BTC-e, had defrauded over 100 people in six French cities between 2016 and 2018.

He is sought for extortion, money laundering and crimes committed online, the court source said.

Vinnik has been held in jail since his arrest last July in the northern Greek tourist resort of Halkidiki. He denies the accusation.

He was indicted by a US court last year on 21 charges ranging from identity theft and facilitating drug trafficking to money laundering.

Greece's Supreme Court in December said Vinnik should be extradited to the US, but the final decision is up to the Greek justice minister.

Russia has also filed a demand to extradite Vinnik so he can stand trial on separate fraud charges.

BTC-e, founded in 2011, became one of the world's largest and most widely used digital currency exchanges.

According to the US indictment, it was "heavily reliant on criminals".

In addition, BTC-e "was noted for its role in numerous ransomware and other cyber-criminal activity".

It allegedly received more than $4 billion (3.5 billion euros) worth of Bitcoin over the course of its operation.

Vinnik was also charged with receiving funds from the infamous hack of Mt. Gox -- an earlier digital currency exchange that eventually failed, in part due to losses attributable to hacking.

The US Treasury Department has slapped BTC-e with a $110 million fine for "wilfully violating" US anti-money laundering laws. Vinnik himself has been ordered to pay $12 million.

In Russia, Vinnik is wanted on separate fraud charges totalling 9,500 euros.

He has said he would accept extradition to his home country.

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