The US on Saturday conducted strikes against Houthi anti-ship cruise missiles and vessels, including on the first unmanned underwater vessel the Iranian-backed rebel group has used since the attacks in the Red Sea began, according to US Central Command.

The US conducted five strikes against three anti-ship cruise missiles, one unmanned underwater vessel and one unmanned surface vessel between 3 and 8 p.m. Saturday local time, CENTCOM said.

“CENTCOM identified the anti-ship cruise missiles, unmanned underwater vessel, and the unmanned surface vessel in Houthi-controlled areas of Yemen and determined they presented an imminent threat to U.S. Navy ships and merchant vessels in the region,” Central Command said in a statement Sunday.

The unmanned underwater vessel attack marks a new strategy for the Houthis and comes in spite of continued US airstrikes against the rebel group. Earlier this month, the US and UK struck at least 30 Houthi targets across at least 10 locations in Yemen with the aim to “de-escalate tensions and restore stability in the Red Sea.”

The Houthis have been attacking US targets and commercial shipping in the Red Sea since Israel launched its invasion of Gaza following Hamas’ October 7 attack. There are fears that the attacks could escalate Israel’s war against Hamas into a wider regional conflict.

The Houthi attacks have forced some of the world’s biggest shipping and oil companies to suspend transit through one of the most important maritime trade routes, which could potentially cause a shock to the global economy.

CNN last week was on board two vessels spearheading the US response to Houthi attacks in the southern Red Sea as the Navy works at a frenetic pace deploying jets and firing missiles at a moment’s notice to try to destroy the Houthis’ weapons and infrastructure.

Yemen rebels claim latest Red Sea vessel strike

The rebels have also vowed 'response and punishment' after the US and British strikes, and say they are acting in solidarity with 'the Palestinian people'

Yemen's Iran-backed Huthi rebels on Saturday claimed an attack a day earlier on an oil tanker in the Red Sea, the latest in a series of strikes which have led to retaliation by Britain and the United States.

The Huthis said the vessel was British, although the US military later said it was Danish.

Huthi naval forces "carried out an operation targeting the British oil tanker Pollux in the Red Sea" with missiles, rebel spokesman Yahya Saree said in a statement.

He did not say how the rebels had determined a "British" connection to the ship.

The US Central Command (CENTCOM) confirmed that four anti-ship ballistic missiles were launched from Huthi-controlled areas of Yemen, between Friday afternoon and 1:00 am (2200 GMT) on Saturday.

"At least three of the missiles were launched towards... MT Pollux, a Panamanian-flagged, Denmark-owned, Panamanian-registered vessel," CENTCOM said in a statement on social media.

It added that it had "successfully conducted two self-defence strikes against one mobile anti-ship cruise missile and one mobile unmanned surface vessel" in Yemen, which it said "presented an imminent threat to US Navy ships and merchant vessels in the region".

The strike came on the same day that Washington's redesignation of the Huthis as a terrorist group and accompanying sanctions came into force.

A US State Department spokesperson said on Friday the vessel was able to continue on its voyage.

The tanker "sustained minor damage" in the missile strike northwest of Yemen's port of Mokha, security firm Ambrey said.

The latest attack came after the US military said earlier on Friday it conducted strikes "against three mobile anti-ship cruise missiles in Huthi-controlled areas of Yemen that were prepared to launch against ships in the Red Sea".

In December the United States announced a maritime security initiative, Operation Prosperity Guardian, to protect shipping in the area.

Repeated strikes on Huthi targets by the United States and Britain have failed to halt the rebel attacks.

The group says it is targeting vessels linked to Israel, in solidarity with the Palestinians in Gaza, where Israel is fighting a bloody war against Hamas in retaliation for its October 7 attack.

The attacks have caused significant disruption to international shipping, with many companies choosing to divert their vessels thousands of kilometres (miles) around the southern tip of Africa to avoid the Red Sea.

At war with Yemen's internationally recognised government since 2014, the Huthis control the capital Sanaa and large parts of the north, including most large population centres.

European Union foreign ministers will meet on Monday in Brussels to formally launch a naval mission of their own to help protect international shipping in the Red Sea against Huthi attacks, officials said on Friday.

What it's like aboard a US warship on the frontlines of the Red Sea fight

Just a few yards away from where I'm is standing on the frenetic flight deck of the USS Dwight D. Eisenhower, an F-18 Super Hornet carefully maneuvers into position on the runway for take off on a mission across the Red Sea.

Its powerful engines growl louder and louder with every second as the crew on deck lock the plane's front gear into a propelling shuttle.

The plane is now at full throttle as the signaling officer lunges forward, extending his right arm out and giving the pilot permission to launch.

The plane shoots forward in a flash, ripping and roaring across the runway while leaving behind a trail of steam rising from the tarmac.

This is the front line of the United States and its allies' response to attacks here in the Red Sea by Iran-backed Houthi rebels in Yemen.

The Houthis have been firing at merchant ships in this passageway, causing major shipping companies to diverge their vessels away from this vital shipping route that provides passage for an estimated 12% of global trade every year, according to the United Nations Conference on Trade and Development.

Commanding Officer Melanie Ahle's job is to respond to distress calls from ships in the area.

"It's definitely a high operations tempo," the VAW-123 squadron leader said. "We're on call 24/7."

A short helicopter ride away from the Eisenhower, I'm given a tour of a guided missile destroyer, the USS Gravely, a critical piece of weaponry at the sharp tip of U.S. engagement with the Houthis. These assault ships are launching near-daily preemptive strikes on Houthi targets.

"This is where we fight from," said Lieutenant JG James Rodney, standing between rows of screens and colorful switches.

The officers here stare hawkishly at the radars in front of them. Their readiness is palpable. Rodney tells me they have minutes, sometimes just seconds, to react to a possible incoming threat.

Naval officers are keen to express their effectiveness in diminishing the Houthis' capabilities since the U.S. began retaliatory strikes more than a week ago.

Rear Admiral Marc Miguez tells us that "numerous strikes" on Houthi positions from the Eisenhower and other ships in Carrier Strike Group Two are successfully degrading the Houthis' capabilities to launch their attacks.

Miguez says he can't predict exactly how long the Houthis will be able to sustain their drone and missile attacks, but that "they're not going to be able to do this forever."

The residual fact is that these attacks have actually made the Houthis far more popular inside Yemen. Their longevity in this fight will depend on how steady the stream of weapons and intelligence supply continues from Iran.

"We know that's happening," Miguez said, "and we continue to monitor it and continue to interdict when we can."

But for those on board the Eisenhower, this is a long slog. Miguez told me it's been months since the ship's last port visit, making it an unusually long time out at sea, with no clear end in sight to the game of cat-and-mouse in these troubled waters.