The U.S. military conducted new airstrikes targeting Yemen’s Houthi rebels, officials said Friday.

American forces destroyed four explosive-loaded drone boats and seven mobile anti-ship cruise missile launchers Thursday that could target vessels in the Red Sea, the U.S. military’s Central Command said.

“They presented an imminent threat to U.S. Navy ships and merchant vessels in the region,” Central Command said. “These actions will protect freedom of navigation and make international waters safer and more secure for U.S. Navy and merchant vessels.”

The Houthis have not acknowledged the losses.

Since November, the rebels have repeatedly targeted ships in the Red Sea over Israel’s offensive in Gaza. But they have frequently targeted vessels with tenuous or no clear links to Israel, imperiling shipping in a key route for trade among Asia, the Mideast and Europe.

In recent weeks, the United States and the United Kingdom, backed by other allies, have launched airstrikes targeting Houthi missile arsenals and launch sites for its attacks.