The Houthis have waged a campaign against international shipping to show solidarity with the Palestinian people, firing drones and missiles at ships in the Red Sea, a vital route for international trade.

The emailed warnings sent to the German industry body and cargo carriers in recent months were "attempts at intimidation", VDR executive Irina Haesler said.

The threats were "directed against ships that call at Israeli ports, as well as against those that pass through the Red Sea, the Bab al-Mandab Strait, the Gulf of Aden, the Arabian Sea and the Indian Ocean", the association said.

"Regardless of their location, ships with supposed links to Israel are considered potential targets," it said.

Anger over Israel's brutal war on the Gaza Strip, which began on 7 October 2023 and has killed at least 43,922 people and injured nearly 104,000, has stoked retaliation from groups in Lebanon, Iraq, Syria, and Yemen.

One such email from the Houthis, seen by AFP, warned German shipowners of "a naval blockade on the Israeli enemy".

It said "all vessels belonging to it, associated with it or bound for it" would be "subject to punishment and ... prohibited from crossing the area of operations of the Yemeni Armed Forces".

A VDR spokeswoman told AFP the authenticity of the emails had been confirmed by the German navy and International Chamber of Shipping.

Most major shipping companies are avoiding the Red Sea and making the longer and more costly journey around Africa.

The United States and other countries have deployed military vessels to help shield shipping from Houthi strikes and carried out repeated air strikes on bases in Yemen.

* This story was edited by Ahram Online.