The U.S. said that two cargo ships in the Red Sea were attacked by missiles and drones fired from Yemeni territory.

According to BBC News, one ship was hit by a drone while the other was hit by a missile. Both attacks came from a part of Yemen controlled by Houthis, a rebel movement backed by Iran.

"We are aware that something launched from a Houthi-controlled region of Yemen struck this vessel which was damaged, and there was a report of a fire," a U.S. defense official told a news agency December 15.

The container ship that was attacked, called the Al Jasrah, is owned by Hapag-Lloyd and flagged to Liberia. A Hapag-Lloyd spokesperson said that the vessel was destined for Singapore from Greece. He added that there were no casualties from the attack, and the ship is once again headed to Singapore.

Later the same day, a U.S. defense official said that a ballistic missile hit a second Liberian-flagged vessel in the Bab El Mandab strait. That missile strike caused a fire onboard the ship, though there were no casualties.

Jake Sullivan, the U.S. national security adviser, said Houthis are a “material threat” to commerce and shipping operations in the Middle East. He also said that Iran bore responsibility for the attacks, saying "While the Houthis are pulling the trigger, so to speak, they're being handed the gun by Iran. Iran has a responsibility to take steps themselves to cease these attacks, because these attacks, as I said before, are a fundamental threat to international law and international peace and security."