(Reuters) – The United States struck up to 10 unmanned drones in Yemen that were preparing to launch, a U.S. official said late on Wednesday, amid escalating tensions from the war in Gaza spreading through the region.

The Iran-aligned Houthi militants, who control the most populous parts of Yemen, have launched a wave of exploding drones and missiles at commercial vessels in the Red Sea and Gulf of Aden in recent weeks, calling it a response to Israel’s military operations in Gaza and a show of solidarity to Palestinians.

The Houthi campaign has disrupted international shipping.

The United States and Britain have launched strikes on Houthi targets in Yemen and returned the militia to a list of “terrorist groups.”

The Houthis, earlier on Wednesday, said their naval forces carried out an operation targeting an “American merchant ship” in the Gulf of Aden hours after firing missiles at U.S. Navy destroyer Gravely.

Houthi attacks on ships in and around the Red Sea have slowed trade between Asia and Europe, raised fears of supply bottlenecks and alarmed major powers concerned that the Gaza war may become a regional conflict.

U.S. President Joe Biden said earlier in January that strikes on Houthi targets would continue even as he acknowledged they may not be halting their attacks.

Israel’s assault on the Hamas-run Gaza Strip followed a surprise attack by Hamas militants on southern Israel on Oct. 7, killing 1,200. The Gaza health ministry says nearly 27,000 people have been killed in the fighting since.