Moscow said Friday that it was preparing a "judicial response" to official asset freezes overseas, after state accounts and property were reportedly blocked in Belgium and France over legal claims from former Yukos shareholders.
"Russia is working on it. What our response will be -- time will tell," deputy foreign minister Vasily Nebenzya told Interfax news agency, adding that "whoever acts like this has to understand that there will be a counter reaction."
A representative of claimants from the defunct oil firm said Thursday that official accounts and buildings had been frozen in the two countries.
In Belgium, accounts of the Russian embassy in Brussels and representative offices at the European Union and NATO headquarters were among those affected, the Russian foreign ministry said.
Moscow summoned the Belgian ambassador to explain the move and threatened "reciprocal measures targeting Belgian assets in Russia".
The Belgian foreign ministry said the seizures had been conducted by bailiffs without the involvement of the Belgian government.
In France, accounts in around 40 banks were frozen along with eight or nine buildings, Tim Osborne, executive director of the main shareholder GML, told AFP.
There was no immediate confirmation of the asset freezes in France from officials in Moscow or Paris.
Yukos was once Russia's biggest oil company but was broken up after the arrest of its owner, Kremlin critic Mikhail Khodorkovsky, in 2003.
That came shortly after President Vladimir Putin warned Russia's growing class of oligarchs against meddling in politics.
Khodorkovsky was granted residency in Switzerland after being released in 2013 following a decade in prison after a presidential pardon from Putin.
Last year, the Permanent Court of Arbitration in The Hague ruled that Moscow had forced Yukos into bankruptcy with excessive tax claims before selling its assets to state-owned firms.
It ordered Russia to pay Yukos shareholders a record $50 billion (44 billion euros) in compensation.
Russia was told 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.
GML's Osborne said that proceedings were "already underway in Britain and the United States and further countries will follow".
He explained that legislation in Belgium and France made it easier to freeze assets pending the outcome of the Yukos compensation dispute.