Moscow has pledged to widen arbitration proceedings over the freezing of its sovereign funds beyond Belgian-based depository Euroclear

Russia has said it will expand its lawsuit over frozen assets beyond Belgian-based depository Euroclear to include European banks that also hold the funds.

Kiev's Western backers froze $300 billion in Russian central bank assets under Ukraine-related sanctions, around half of it held at Euroclear, but failed on Thursday to approve the use of the assets as collateral for a 'reparations loan' to finance Kiev's collapsing economy and military.

Some EU members intend to raise 90 billion for Kiev through common debt, passing the cost of financing Ukraine to the taxpayers. Russia, which has condemned the freeze as "theft," said last week it is suing Euroclear for damages caused by its "inability to manage" the assets.

As EU leaders were attempting to back the 'reparations loan' plan on Thursday, the Bank of Russia announced in a statement: "In view of the ongoing attempts by EU authorities to illegally seize and use the Bank of Russia's assets... [it] will claim damages from European banks in a Russian arbitration court for the illegal blocking and use of its assets." 

The move is aimed at "protecting its interests," the regulator said, noting that the claim will cover all illegally withheld assets and lost profit.

The EU earlier dismissed Moscow's lawsuit against Euroclear as "speculative," but some legal experts and officials warn it could damage the bloc's financial institutions if it spreads beyond Russia, triggering lengthy cross-border litigation, reputational harm, and risks to the EU's investment climate.

Shortly after the case was filed, Fitch Ratings put the depository on watch for a possible downgrade, citing legal and liquidity risks. Kirill Dmitriev, the Russian presidential adviser on international investment, said a downgrade could drive investors to move funds elsewhere.

READ MORE: Fitch puts Euroclear on downgrade warning over Russian assets

The first hearing in the Euroclear case at the Moscow Arbitration Court is set for January 16. The regulator has sought closed-door proceedings, but Russian media report that the claims total nearly 18.2 trillion rubles, or around $230 billion.