Yemeni fighters from the Houthi movement said they will close Saudi Arabia’s coast starting Monday. Their spokesman, Yahya Saree, called it a naval attack. Merchant ships moving through the Red Sea near Saudi ports may encounter holdups. U.S. warplanes continued striking objectives after their warning. The group seized several ships. Insurers now see Red Sea routes as hazardous. Traders are waiting anxiously, watching for higher fees or diverted shipments. Saudi ports are close to the risk area, so any delay is critical quickly.