DUBAI, United Arab Emirates >> U.S. long-range B-2 stealth bombers launched airstrikes early Thursday morning targeting underground bunkers used by Yemen’s Houthi rebels, officials said.

However, there are no previous reports of the B-2 Spirit being used in the strikes targeting the Houthis, who have been attacking ships for months in the Red Sea corridor over the Israel-Hamas war in the Gaza Strip.

The Houthis’ al-Masirah satellite news channel reported airstrikes around Yemen’s capital, Sanaa, which the group has held since 2014. They also reported strikes around the Houthi stronghold of Saada. They offered no immediate information on damage or casualties.

U.S. Defense Secretary Lloyd Austin said in a statement that the B-2 bombers targeted “five hardened underground weapons storage locations in Houthi-controlled areas of Yemen.”

The strike also appeared to be an indirect warning to Iran, the Houthis’ main benefactor, which has targeted Israel with ballistic missile attacks twice over the past year. The B-2 would be used in any American attack on hardened Iranian nuclear facilities given it is the only aircraft in service that can drop the GBU-57, known as the “Massive Ordnance Penetrator.”

Austin and the U.S. military’s Central Command offered no immediate assessment on the damage done. However, Central Command said in a statement that initial assessments suggested no civilians had been killed.