The U.S. Navy seized more than 2,000 assault rifles from a fishing boat Friday that were most likely bound for Iranian-backed rebels in Yemen, U.S. Central Command said in a statement.

The vessel, crewed by six Yemenis, was sailing on a route through the Gulf of Oman often used to traffic illicit cargo to the Houthi rebels when it was boarded by U.S. sailors, who seized the 2,116 AK-47 rifles.

“This shipment is part of a continued pattern of destabilizing activity from Iran,” said Vice Adm. Brad Cooper, the commander of U.S. Naval Forces Central Command, U.S. 5th Fleet and Combined Maritime Forces. “These threats have our attention. We remain vigilant in detecting any maritime activity that impedes freedom of navigation or compromises regional security.”

On Dec. 1, the U.S. seized more than 50 tons of ammunition, fuses and rocket propellant from a fishing vessel in the Gulf of Oman, which separates the southern part of the Arabian Peninsula from Iran.

A month earlier, the Navy and the Coast Guard intercepted an enormous Iranian shipment of explosive materials headed to Yemen, according to U.S. Central Command.

The stateless fishing boat was carrying more than 180 tons of urea fertilizer and ammonium perchlorate when the Coast Guard ship USCGC John Scheuerman and the Navy guided missile destroyer USS The Sullivans came across the dhow in the Gulf of Oman on Nov. 8.

After U.S. military explosives experts examined the boat and off-loaded the explosive material and Yemeni crew members, the U.S. military deemed the boat a hazard to commercial ship navigation and sank it.

Iran has long supported the mostly Shiite Houthi rebels, who control much of northern Yemen and are engaged in an ongoing conflict with Saudi Arabia.