The U.S. and British militaries launched a fresh round of strikes against Houthi targets in Yemen on Monday, defense officials said.

The attacks, which were carried out by manned aircraft and ships, were the second round of strikes the two militaries have launched against Houthi sites in Yemen. The last round was on Jan. 11. Since then, the U.S. has struck several Houthi targets on its own to prevent the group from attacking ships in the Red Sea.

U.S. Central Command said in a statement that the latest operation, which was supported by Australia, Bahrain, Canada and the Netherlands, struck eight Houthi sites in Yemen “used to attack international merchant vessels and U.S. Navy ships in the region.”