"It's bank accounts and real estate," Tim Osborne, executive director of main shareholder GML, told AFP, adding that accounts in around 40 banks had been frozen along with "eight or nine buildings".
He said the asset freeze occurred two weeks ago but had only been "leaked" by Russia on Thursday. There was no immediate official confirmation from Moscow or Paris.
"Proceedings are already under way in Britain and the United States and further countries will follow," he said, following a move by Belgium to freeze Russian government accounts which sparked anger in Moscow.
The Permanent Court of Arbitration in The Hague ruled last year that Moscow had forced Yukos -- once owned by Kremlin critic Mikhail Khodorkovsky -- into bankruptcy with outsized tax claims before selling its assets to state-owned firms.
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Russia was ordered to pay compensation to shareholders to subsidiaries of Gibraltar-based Group Menatep, through which Khodorkovsky ran Yukos.
The group exists today as holding company GML, although Khodorkovsky is no longer involved and is not a party to the compensation claim.
It was sold off in opaque auctions between 2004 and 2006.
Khodorkovsky was granted residency in Switzerland after being released in 2013.