Israel said on Sunday that Yemen’s Houthis had seized a British-owned and Japanese-operated cargo ship in the southern Red Sea, describing the incident as an “Iranian act of terrorism” with consequences for international maritime security.

The Houthis said they had seized a ship in that area but described it as Israeli. “We are treating the ship’s crew in accordance with Islamic principles and values,” a spokesperson for the group said, making no reference to the Israeli account.

The Houthis, an ally of Tehran, have been launching long-range missile and drone salvoes at Israel in solidarity with the Palestinian Hamas militants fighting in the Gaza Strip.

Japan’s top government spokesperson on Monday confirmed the capture of the Nippon Yusen-operated ship, Galaxy Leader, adding that Japan was appealing to the Houthis while seeking the help of Saudi, Omani and Iranian authorities to work toward the swift release of the vessel and its crew.

“We strongly condemn such acts,” Chief Cabinet Secretary Hirokazu Matsuno told a news conference. No Japanese nationals are among the crew, he said.

Galaxy Leader is owned by a company registered under Isle of Man-headquartered Ray Car Carriers, which is a unit of Tel Aviv-incorporated Ray Shipping, according to LSEG data.

Ray Car Carriers and Ray Shipping could not be immediately reached for comment outside business hours.

Japan’s Nippon Yusen (9101.T), also known as NYK, said the company had set up a task force to gather more information, including on the safety of the 25 crew, who are from the Philippines, Bulgaria, Ukraine, Romania and Mexico. The vessel, a car carrier, had been heading toward India from Europe with no cargo, a spokesperson said.

Last week, Houthi leadership said their forces would make further attacks on Israel and they could target Israeli ships in the Red Sea and the Bab al-Mandeb Strait.

The U.S. was monitoring the situation, a defence official said.

Israeli Prime Minister Benjamin Netanyahu’s office said a ship – which it did not name – had been seized. There were no Israelis aboard and Israel was not involved in its ownership or operation, his office said.

“This is another Iranian act of terrorism that represents an escalation in Iran’s belligerence against the citizens of the free world, with concomitant international ramifications vis-a-vis the security of global shipping routes,” his office said.

Earlier on Sunday the Houthis said all ships owned or operated by Israeli companies, or carrying the Israeli flag, could be targeted.