US B-2 stealth bombers used to strike Houthi bunkers deep underground in Yemen

US B-2 stealth bombers have been used against the Iran-backed Houthis for the first time in an escalation of Washington’s response to attacks on shipping in the Red Sea that serves as a message to Tehran.

It is believed to be the first time the B-2 has been used in a combat mission since 2017. In announcing the strikes against the Houthis, the US defence secretary, Lloyd Austin, made a point of issuing a warning that there will be no place that Washington cannot reach.

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

The “hardened” facilities contained weapon components which the Houthis have used to “target civilian and military vessels throughout the region”, Mr Austin said, but it is not yet clear how much damage has been caused.

Iran, the Houthis’ main benefactor, 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 like Natanz or Fordo, given it is the only aircraft in service that can drop the GBU-57, known as the “Massive Ordnance Penetrator”.

The Houthis’ Al Masirah news channel reported airstrikes around Sana’a, Yemen’s capital, which the militant group has held since 2014. The channel did not give information on damage or casualties.

The Houthis have targeted more than 80 merchant vessels with missiles and drones since the war in Gaza started in October 2023. They have seized one vessel and sunk two in the campaign that has also killed four sailors. Other missiles and drones have either been intercepted by a US-led coalition in the Red Sea, which also includes the UK, or failed to reach their targets, which have included Western military vessels.

The Houthis maintain that they target ships linked to Israel, the US or the United Kingdom to force an end to Israel's campaign against Hamas in Gaza. However, many of the ships attacked have little or no connection to the conflict, including some bound for Iran.

The Houthis also continue to launch missiles targeting Israel and have shot down US military MQ-9 Reaper drones. They have threatened new attacks in response to Israel's ground invasion of Lebanon and its killing of the Tehran-backed Hezbollah’s leader Hassan Nasrallah.

In February, after months of firing at ships linked to Israeli allies, the Houthis announced they had “banned” vessels linked to Israel, the US and the UK from sailing in the seas surrounding Yemen. Houthi leader Abdulmalik al-Houthi said at the time they had introduced “submarine weapons” into their arsenal.

Some shipping companies have been forced to suspend services in the Red Sea, which usually sees an annual flow of goods worth $1 trillion passing through.

Earlier this month, the US military carried out 15 strikes against Houthi targets in Yemen, with residents reporting explosions at military outposts and in an airport. The Pentagon said it had launched the attacks to “protect freedom of navigation”.