In the most significant blow yet to the Iran-backed Houthis, the United States announced a sweeping set of sanctions targeting entities, individuals and vessels that generate critical revenue for the group’s activities.

The United States has imposed sanctions against Houthis on four individuals, 12 entities, and two vessels, for their alleged role in the import of oil and other illicit goods in support of the group.

These targets include Houthi front companies, their owners, and other key Houthi operatives allegedly involved in the sale of oil and other commodities on Yemen’s black market and in smuggling operations through Houthi-controlled ports.

The U.S. Department of the Treasury’s Office of Foreign Assets Control (OFAC) is targeting two vessels, as well as their owners and operators, accusing them of violating U.S. sanctions by discharging oil derivatives to the Houthis.

“The Houthis rely on a series of front companies and trusted facilitators to clandestinely generate revenue, procure weapons components, and advance their reign of terror in partnership with the Iranian regime,” said deputy secretary of the treasury Michael Faulkender.

“Today’s action – our most significant to date against the group – underscores our commitment to disrupting the Houthis’ financial and shipping pipelines that enable their reckless behavior in the Red Sea and the surrounding region.”

OFAC said on Friday the vessels targeted continued to support the Houthis through the discharge of refined petroleum products at Houthi-controlled ports.

The penalties aim to block them from using the U.S. financial system and prohibit American citizens from dealing with them.

As reported, violations of U.S. sanctions may result in the imposition of civil or criminal penalties on U.S. and foreign persons.

OFAC clarifies in its statement that “by providing material support to the Houthis not only carries acute sanctions risk, but also exposes vessels and crew members to serious safety risk from potential Houthi attacks.”