MOSCOW, July 12 (Reuters) - One of Russia's oldest asset managers, First AM, has filed a claim for 184.8 billion roubles ($2.04 billion) with the Moscow Arbitration Court against Euroclear Bank, court documents showed, trying to protect investors whose assets were frozen.

Sanctions on Russia's National Settlement Depository (NSD), as well as other Western measures aimed at restricting Russia's access to global financial infrastructure, have blocked many Russian investors' access to securities held in jurisdictions outside Russia.

First AM, formerly known as Sber Asset Management, had 1.44 trillion roubles in assets under management as of September 2022. It said it was trying to use every available opportunity to protect its clients' interest.

"We have filed a lawsuit...to protect the rights and interests of our clients, whose assets were frozen," First AM told Reuters. "The defendant is the European central depositary Euroclear. In 2022, it blocked Russian investors' operations on assets which were accounted for in the NSD account."

Belgium-based Euroclear did not immediately respond to a request for comment.

Euroclear has previously said various counterparties from Russia have turned to the courts in Russia and the European Union to challenge it in a bid to recover frozen payments. The Kremlin says Russia and its entrepreneurs have been robbed by Western asset freezes.

In case these lawsuits have any material impact, the company has said it had decided to separate its sanctions-related earnings from its underlying financial results when evaluating its own performance and resources.

Euroclear, a core part of the global securities settlement system, posted a record year in 2022 after cutting ties with Russian customers, boosted by interest on Russian cash that it is holding.

Late last year, First AM applied to European authorities to unblock its assets at Euroclear and Clearstream. It has also applied to the finance ministries of Belgium and Luxembourg directly.

($1 = 90.5500 roubles) (Reporting by Elena Fabrichnaya and Alexander Marrow; Editing by Sharon Singleton)