Some commercial ships are emailing Yemen’s Houthis for permission before passing through the Bab al-Mandab Strait, The Wall Street Journal reported, citing crew members and emails it had reviewed. The strait, between Yemen and the Horn of Africa, is the narrow gateway to the Red Sea.

The requests go to the Humanitarian Operations Coordination Center, a body the Houthis set up in early 2024 to enforce their restrictions on shipping. In the messages, ship operators declare that their vessels, owners and crews have no links to Israel, the United States or Britain, and give their routes and expected arrival times.

In one email, a ship’s master wrote that the vessel “has no connections with Israel, the United Kingdom and the United States of America” and asked for “confirmation for safe passage.” The Houthis usually reply within 24 hours, the newspaper said.

In one case, the center gave the Chinese container ship Zhong Cheng Chang Ling a permit valid for seven days and told it to keep its Automatic Identification System switched on and to monitor the VHF Channel 16 distress frequency during the transit.

Requests grew after the Houthis declared a ban on shipping to and from Saudi ports in July, as fighting between the group and Saudi Arabia resumed. Ships seen as linked to the three Western countries have been attacked by the Houthis in past years.

International maritime security bodies advise ships not to register with or contact the Houthi center, and many vessels do not. The United States designates the Houthis as a foreign terrorist organization, and maritime officials have warned that dealing with the group could breach sanctions. The Houthis said on Friday that 1,083 ships passed through the strait in October, 550 heading north and 533 heading south, and called it proof that international navigation was continuing normally. The figures could not be independently verified.