The US Treasury Department on Monday imposed new sanctions on Russia's state-controlled VTB Bank over allegations that it helped Iran evade sanctions, CNBC reported Monday.

The action targets VTB's correspondent relationships with sanctioned Iranian banks and is expected to block at least tens of millions of dollars, CNBC said.

The Treasury described VTB, Russia's second-largest bank, as among the most comprehensively sanctioned financial institutions in the world, the report said.

The sanctions are part of the Trump administration's "Operation Economic Outcast" effort to economically isolate Iran, CNBC said.