Yemen's Houthi movement said on Saturday they would target all ships heading to Israel, regardless of their nationality, and warned all international shipping companies against dealing with Israeli ports.
The Iran-aligned group is escalating the risks of a regional conflict amid a brutal war between Israel and the Palestinian militant group Hamas.
The Houthis have attacked and seized several Israeli-linked ships in the Red Sea and its Bab al-Mandab strait, a sea lane through which much of the world's oil is shipped, and fired ballistic missiles and armed drones at Israel.
Houthi officials say their actions are a show of support for the Palestinians.
Israel said attacks on ships was an "Iranian act of terrorism" with consequences for international maritime security.
A Houthi military spokesperson said all ships sailing to Israeli ports are banned from the Red Sea and the Arabian Sea.
"If Gaza does not receive the food and medicine it needs, all ships in the Red Sea bound for Israeli ports, regardless of their nationality, will become a target for our armed forces," the spokesperson said in a statement.
The threat has an immediate effect, the statement added.
The Houthis are one of several groups in the Iran-aligned "Axis of Resistance" which have been hitting Israeli and U.S. targets since Oct. 7 when Hamas militants attacked Israel.
In one of the latest incidents, three commercial vessels came under attack in international waters last week, prompting a U.S. Navy destroyer to intervene.
The Houthis, which rule much of Yemen and its Red Sea coast, also seized last month a British-owned cargo ship that had links with an Israeli company.
The United States and Britain have condemned the attacks on shipping, blaming Iran for its role in supporting the Houthis. Tehran says its allies make their decisions independently.
Saudi Arabia has asked the United States to show restraint in responding to the attacks.
(Reuters - Reporting by Mohammed Alghobari, writing by Aziz El Yaakoubi; Editing by Nick Macfie and Clelia Oziel)