The U.S. early Thursday carried out a “self-defense” strike, targeting and destroying multiple projectiles that Houthi militants in Yemen were preparing to launch at commercial ships, a U.S. official tells Fox News.

The strike marks the 12th time the U.S. has conducted strikes against the Houthis in Yemen since January 11th, and the second in under 24 hours. The U.K. was not involved in this strike, and it was carried out unilaterally by the U.S.

Thursday morning’s strike is not related to Sunday’s drone attack that killed three U.S. soldiers and injured more than 40 others at a base in Jordan.

The latest strike came after the U.S. struck a Houthi anti-aircraft surface-to-air missile that was preparing to launch from a Houthi-controlled area of Yemen. A U.S. official said the surface-to-air missile was on the ground and “posed an imminent threat” to U.S. aircraft patrolling the area.

Houthi militants, based in Yemen, have for weeks been firing upon commercial ships in the Red Sea. The soldiers say the strikes have been a show of support for Palestinians killed in the ongoing Israel-Hamas war in Gaza.

The attacks have caused ships to avoid the Red Sea and reroute, adding tremendous costs and delays. Since early December, ship volumes have plummeted in the area with nearly 40% fewer vessels passing through the canal, leading to a 45% decline in freight tonnage.