Yemen's Houthi movement has announced new restrictions on shipping activity linked to Saudi Arabian ports, issuing warnings directly to companies operating in the maritime sector.

They announced what they described as a maritime embargo against the Gulf country and warned that vessels violating the blockade could be targeted.

According to a Reuters report, an email was sent on 20 July by the rebel group to multiple shipping companies, stating that vessels are prohibited from loading or discharging cargo at any Saudi port.

Shortly after the announcement, Lloyd’s List reported that COSCO Shipping's vehicle carrier had become the first vessel tracked making a U-turn in response to the Houthis' blockade.

Later on Wednesday, 22 July, Lloyd’s List added that more crude carriers decided to reroute away from the Red Sea to avoid being caught in the conflict.

Maritime consultancy firm Ambrey assessed Saudi-flagged, owned or operated vessels, ships travelling to or from Saudi Arabia, and vessels linked to the kingdom's Red Sea ports as having a strong association with the Houthi target profile.

The company said the maritime domain had not yet been directly affected following the announcement, but highlighted an increased risk and advised shipping companies to review affiliations and reconsider higher-risk transits.

Saudi Arabia's foreign ministry rejected separate accusations that the kingdom was blockading Yemen and said it would take all necessary measures to safeguard its vessels under international law and the 1982 United Nations Convention on the Law of the Sea.

EU calls on ships to avoid the Red Sea

The latest warnings come as attention remains focused on shipping activity in and around the Red Sea, where traffic has not fully recovered since attacks on merchant vessels began in November 2023.

The threats by the Houthis prompted US President Trump to comment on 21 July, stating that his country would respond if the movement follows through on its threat to impose a blockade on commercial shipping in the Red Sea.

Meanwhile, the European Union’s naval mission, European Union Naval Force, issued an advisory, raising its threat assessment for the area and recommending that commercial vessels linked to Israel, the US or Saudi Arabia avoid activities in the Gulf of Aden.

The agency advised on every vessel that is currently operating in the area to "reduce its electronic footprint by minimising AIS (ship-tracking) transmissions and limiting any publicly accessible digital information that could facilitate targeting."

At the time of writing this article, no announcements or changes to ocean services were made by any of the major container liners.