AP Moller-Maersk A/S halted transit through the Red Sea after an attack on one of its ships by Houthi rebels led to a significant escalation of tensions in the vital waterway.

The world’s No. 2 container line is suspending all Red Sea transit for 48 hours to assess the security situation. The US Navy said it was fired upon when responding to a distress call from the Maersk Hangzhou, resulting in the sinking of three Houthi boats and the death of their crews.

The latest attack undermines efforts by Washington to reassure shipping companies that it’s safe to sail through the Suez Canal and Red Sea, a passageway for nearly 12% of global commerce. The US set up Operation Prosperity Guardian to secure navigation as Yemen-based Houthi rebels show no signs of stopping attacks designed to pressure Israel into a cease-fire in Gaza.

Yahya Saree, a spokesman for Houthi forces, warned all countries of “grave” consequences if they participate in the US-led maritime coalition.

In a televised statement on Sunday, preceded by anti-American propaganda videos and slogans, Saree said 10 members of the group were dead or missing.

He said the ship was headed toward Israel and that the US interfered with the group’s “humane and moral duty” to stop it. He urged Yemenis and “free” Arabs and Muslims to be “ready for all options in confronting the American escalation.”

Distress Calls

The US said it received a distress call at 6:30 a.m. Sanaa time from the Maersk Hangzhou — the second from the same vessel in less than 24 hours.

Read More: US Tries to Reassure on Red Sea Shipping as Doubts Persist 

Four small boats originating from Yemen got to within 20 meters of the ship and attempted to board it, US Central Command said in a post on X. Helicopters from the USS Eisenhower and USS Gravely responded with an attack that sunk three boats.

“In the process of issuing verbal calls to the small boats, the small boats fired upon the US helicopters with crew served weapons and small arms,” it said. The fourth boat fled and there was no damage to US personnel or equipment, according to the statement.

The first incident involving the Singapore-flagged and Denmark-owned container ship occurred Saturday evening local time when it reported that it was struck by a missile as it was transiting the Southern Red Sea, Centcom said in an earlier post on X.

Two US destroyers, the USS Gravely and USS Laboon, responded to the container ship’s first distress call. The Graveley shot down two anti-ship ballistic missiles fired from Houthi-controlled areas in Yemen toward the ships, Centcom said in the statement.

A spokeswoman for Maersk confirmed the incidents and said the crew is safe and the vessel continues to transit north. 

“The Houthis are still testing the limits of the US strategy,” said Ryan Bohl, senior Middle East and North Africa analyst at RANE Network. “Each shipping company will have to decide their own risk tolerance given that the US also has a record of successful interceptions like the ones reported today.”

He said even if the US and its allies were to escort every single ship transiting the Red Sea, it would not deter aerial attacks by the Houthis.

Houthi Warning

Military commanders of the Houthi forces, who control a swath of Yemen’s territory including the capital Sanaa and the strategic port city of Al-Hudaydah, held a meeting on the coast Wednesday to plot their next moves. “The commanders discussed options to confront US provocations in the Red Sea,” said the Saba News Agency, which is controlled by the group.

The agency released a photograph which it said was from the Al-Hudaydah meeting showing Houthi commanders, who also hold senior positions in the group’s Sanaa-based government, seated in a conference room with large maps of the Red Sea, Middle East and Israel displayed behind them. 

The Houthis have seized one container ship and launched more than 20 attacks in the Red Sea since mid-November in what they have said was a show of solidarity with Palestinians.

Israel has vowed to press on with its nearly three-months-old war in Gaza until it eradicates Hamas, which launched an unprecedented attack on the Jewish state on Oct 7. More than 21,000 Palestinians have been killed so far, according to health authorities in the Hamas government in Gaza. The United Nations has warned that the enclave’s estimated 2 million people are suffering from severe food shortages and a dire humanitarian situation.

Sunday’s incident underscores that the Houthis’ motives go beyond the war in Gaza, said Farea Al-Muslimi, a Yemen expert with the London-based think tank Chatham House.

“They are praying and hoping for a boxing match with the US, that’s definitely their dream,” he said referring to Houthi aspirations to bolster their regional and global standing as a resistance force to be reckoned with.

The US said last week that Iran was “deeply involved” in the Houthi attacks on ships and that the Yemeni militants rely on monitoring systems provided by Tehran. Iran denied this. 

“I made clear that Iran shares responsibility for preventing these attacks given their long-standing support to the Houthis,” said UK Foreign Secretary David Cameron on X after a call with his Iranian counterpart Hossein Amir-Abdollahian on Sunday. 

Danish Link

Before the attacks on the Maersk Hangzhou, Denmark’s government said it planned to send a frigate by the end of January to join the US-led Red Sea task force. 

Operation Prosperity Guardian was launched on December 19 with Bahrain, Canada, France, Italy, the Netherlands, Norway, Seychelles, Spain and the UK “to jointly address security challenges in the southern Red Sea and the Gulf of Aden.” 

Additional countries are expected to join the task force, US Naval Forces Central Command Vice Admiral Brad Cooper told Associated Press in an interview on Sunday.

Danish Foreign Minister Lars Lokke Rasmussen  declined to draw any linkages between his government’s announcement two days ago and the Houthi attacks on the Denmark-owned ship.

He said Denmark, which is home to the world’s largest shipping firms, was undeterred by the attack and the government would seek to expedite the process of securing parliamentary approval to dispatch the Danish warship to the Red Sea.

“This attack clearly emphasizes how serious the situation unfortunately is now,” he said in emailed remarks.