The US has warned Russian oligarchs and businesses that it is monitoring their financial transactions for any signs of evasion of Ukraine war-related sanctions as well as tracking those offering them “material support”.

A senior US Treasury official said Washington had noted an uptick in efforts by rich Russians and companies to conceal wealth and money transfers in the month since western governments began imposing sanctions on Russia over its war in Ukraine. The US is also tracking those not already subject to sanctions.

Wealthy Russians, who are already well-versed at hiding their assets to evade taxes, were exploiting the “l(fā)eaky” capital controls imposed by Moscow as part of its efforts to prevent a financial system meltdown, the official told the Financial Times.