The United States on Tuesday imposed sanctions on Iran’s central bank governor and an Iraq-based bank for “moving millions of dollars” for Iran’s elite Revolutionary Guard, as Washington seeks to cut off funding it says Tehran is using to fund militant activities overseas, Reuters reported.

U.S. Treasury Secretary Steven Mnuchin accused bank chief Valiollah Seif of covertly funneling money on behalf of the revolutionary guard’s external arm, Quds Force (IRGC-QF), through Al-Bilad Islamic Bank “to enrich and support the violent and radical agenda of Hezbollah.”

The move cuts off Iran’s use of a critical banking network, he said. The United States classifies Lebanon’s Shi’ite Muslim movement Hezbollah, which is backed by Iran, as a terrorist organization.

“It is appalling, but not surprising, that Iran’s senior-most banking official would conspire with the IRGC-QF to facilitate funding of terror groups like Hezbollah, and it undermines any credibility he could claim in protecting the integrity of the institution as a central bank governor,” Mnuchin said in a statement.

Speaking in Brussels, Iran’s Foreign Minister Javad Zarif called the sanctions against Seif illegal.