Israeli ships are a "legitimate target", Yemen's Houthi rebels warned Monday, after their seizure of an Israel-linked cargo vessel opened a new dimension in the Gaza war.
Sunday's capture of the Galaxy Leader and its 25 international crew came days after the Houthis threatened to target Israeli shipping over the Israel-Hamas war.
The Houthis, declaring themselves part of the "axis of resistance", have also launched a series of drones and missiles towards Israel.
"Israeli ships are legitimate targets for us anywhere...and we will not hesitate to take action," Major General Ali al-Moshki, a Houthi military official, told the group's Al-Massirah TV station.
Analysts also said Houthi threats to shipping around the Bab al-Mandab Strait, a choke-point at the foot of the commercially vital Red Sea, were likely to rise.
The Bahamas-flagged, British-owned Galaxy Leader is operated by a Japanese firm but has links to Israeli businessman Abraham "Rami" Ungar.
The Houthis said the capture was in retaliation for Israel's war against Hamas, sparked by the October first week storming by the Palestinian fighters into the country.
More than 13,000 people have since been killed in Israel's aerial bombardment and ground operations in the Gaza Strip, the territory's Hamas-run health ministry says.
Sunday's ship seizure "is only the beginning," Houthi spokesman Mohamed Abdul-Salam said Sunday in a statement posted on X, formerly Twitter, pledging further maritime attacks until Israel halts its Gaza campaign.
Maritime security company Ambrey said it had learned that the rebels boarded the ship by rappelling or sliding down a rope from a helicopter — the method used by Iran during previous vessel seizures in the Strait of Hormuz.
The vessel headed from Turkey to India was re-routed to the Yemeni port of Salif in Hodeidah province, according to Ambrey and a Yemeni maritime source.
Ambrey said the owner of the Galaxy Leader, which transports cars and other vehicles, is listed as Britain's Ray Car Carriers whose parent company belongs to Ungar, the Israeli businessman.
Israel's military said the seizure was a "very grave incident of global consequence", while a US military official called it "a flagrant violation of international law".
The crew were reportedly "under investigation" by the Houthis, Ambrey said. They include Ukrainians, Bulgarians, Filipinos, Mexicans and a Romanian, according to Israeli and Romanian officials.
Nippon Yusen, also known as NYK Line of Japan, said it had set up a task team to gather information and ensure the crew's safety.
Japanese Foreign Minister Yoko Kamikawa said Tokyo was "directly approaching the Houthis" as well as communicating with Israel.
"We are also urging Saudi Arabia, Oman, Iran and other countries concerned to strongly urge the Houthis for the early release of the vessel and crew members," she said.
The office of Israeli Prime Minister Benjamin Netanyahu characterised the capture as an "attack against an international vessel".
"We have repeatedly announced that the resistance groups in the region represent their countries and make decisions and act based on the interests of their countries," said Iran's foreign ministry spokesman Nasser Kanani.
Yemen's coastline overlooks the Bab al-Mandab Strait — a narrow pass between Yemen and Djibouti at the foot of the Red Sea — which is one of the world's busiest shipping lanes, and carries about a fifth of global oil consumption.
"The threat of disruption to shipping in the wider region is likely to rise," said Torbjorn Soltvedt of the risk intelligence firm Verisk Maplecroft.
"If security concerns compel shipping companies to avoid the Bab al-Mandab Strait, the result will be significantly higher costs due to the lack of alternative routes." Mohamed al-Basha, senior Middle East analyst for the US-based Navanti Group said the failure of Houthi missile and drone launches to hit targets inside Israel "might have influenced the decision to refocus on the Red Sea arena".
The Galaxy Leader cargo ship is escorted by Houthi boats in the Red Sea in this photo released Monday.