US B-2 stealth bombers struck weapons storage sites linked to Houthi rebels in Yemen, the latest effort to blunt attacks by the Iran-backed group that have roiled commercial shipping in the Red Sea.

The strikes hit what Defense Secretary Lloyd Austin said in a statement were five hardened underground facilities. He said the use of the B-2 bombers was intended to send a message.

"This was a unique demonstration of the United States’ ability to target facilities that our adversaries seek to keep out of reach, no matter how deeply buried underground, hardened, or fortified," Austin added.