ANKARA (AA) – The US Treasury Department announced Thursday it blocked $1 billion in assets of a Russian oligarch in a trust.

The Delaware-based Heritage Trust, in which Suleiman Abusaidovich Kerimov holds property interest, holds assets of more than $1 billion. It was formed in July 2017 to hold and manage Kerimov’s US-based assets, according to the agency.

“This action ensures that those assets remain blocked and inaccessible to Kerimov,” it said in a statement.

Kerimov’s nephew, Ruslan Gadzhiyevich Gadzhiyev, is a beneficiary of Heritage Trust and his property interest in the trust provides a separate and independent basis for Heritage Trust to be blocked, it said.

“Kerimov used a complex series of legal structures and front persons to obscure his interest in Heritage Trust, the funds of which first entered the US financial system through two foreign Kerimov-controlled entities prior to the imposition of sanctions against him,” it said.

The Treasury Department said the funds were invested in large public and private companies and managed by a series of investment firms and facilitators in the US.

Kerimov and his proxies used various layers of shell companies to conceal his interest, it added.