The Treasury Department said Thursday it has blocked a $1 billion Delaware-based trust connected to sanctioned Russian oligarch Suleiman Abusaidovich Kerimov.

The move comes after the U.S. seized a $325 million superyacht — the 348-foot-long Amadea — tied to Kerimov earlier this month.

The size of the trust and the complexity of the investigation made this a unique case, according to the department.

“Treasury continues using the full range of our tools to expose and disrupt those who seek to evade our sanctions and hide their ill-gotten gains,” Treasury Secretary Janet Yellen said in a statement.

“Even as Russian elites hide behind proxies and complex legal arrangements, Treasury will use our broad enforcement authorities, as well as our partnerships through the REPO Task Force, to actively implement the multilaterally coordinated sanctions imposed on those who fund and benefit from Russia’s war against Ukraine,” she said.

Earlier this year, Treasury, the Justice Department and other agencies convened a task force known as REPO — short for Russian Elites, Proxies and Oligarchs — to work with other countries to investigate and prosecute oligarchs and individuals allied with Russian President Vladimir Putin.

That consortium blocked and froze $30 billion in sanctioned individuals’ property and funds in its first 100 days in operation, the Treasury Department reported Wednesday.

Allied governments have done everything from barring individuals from trading in Russian gold in the U.S. to banning companies from providing accounting, legal and consulting services to anyone located in Russia.

Earlier this week, the Group of Seven nations agreed on a ban on Russian gold imports in the latest round of sanctions over Putin’s invasion of Ukraine.