Swiss banks hold up to $213 billion of Russians' wealth, according the The Swiss Bankers Associaton (SBA).

The bulk of the banks' Russian client money is in Swiss francs, and the revelation is important because Switzerland is the world's biggest location for offshore wealth, the New York Post reports.

"The SBA's revelation is rare for Switzerland, which has stonewalled many previous transparency requests -- and comes as it took the unusual step of applying European Union sanctions to Russian cash following Moscow's invasion of Ukraine last month," the Post writes.

Co-President of Switzerland's Social Democrats Mattea Meyer says reporting the wealth of Russians is important, since it is owned by "oligarchs loyal to the Kremlin [and] helps finance the war."

Meyer adds that it is the responsibility of Switzerland to "do everything possible to turn off the money taps."

Switzerland is not only the world's biggest location for offshore wealth but is known for its secretive bank accounts and tax breaks.