Militants believed to be Iranian-backed Houthi rebels used a helicopter raid to seize a Japanese cargo ship in the southern Red Sea, said three U.S. officials.

According to the officials, at around 1 p.m. Sunday local time, a helicopter hovered over the Galaxy Leader, a Japanese-owned and Bahamian-flagged ship, and several armed individuals rappelled down to the deck.

The attack off the coast of Yemen comes just days after the Houthis issued a graphic with captions in Hebrew, Arabic and English that said, “We will sink your ships.” The graphic showed an Israeli commercial ship on fire.

On Nov. 16, the International Maritime Security Construct, an international group that tries to maintain security in regional waters, issued an advisory to all mariners in the Red Sea and the Bab el-Mandeb trait between Yemen and Djibouti because of the threat, but did not name the Houthis. The advisory warned ships to stay as far away from Yemeni waters as possible and recommended travel at night whenever possible.

A spokesperson for the U.S. Navy’s forces in the region referred a request for comment to the Pentagon.

A U.S. Defense official said, “We’re aware of the situation and are monitoring it closely.”

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A spokesperson for the Israel Defense Forces said via X that, “The hijacking of the cargo ship by the Houthis near Yemen in the southern Red Sea is a very serious event on a global level. This is a ship that left Turkey on its way to India with an international civilian crew, with no Israeli crew members on board. The ship that has been hijacked is not an Israeli ship.”

The Houthis have been fighting the Yemeni military for more than a decade with Iranian backing. Since the beginning of the war between Israel and Hamas, another Iranian proxy, the Houthis have been launching drones and missiles northward.

On Oct. 19, a U.S. Navy warship shot down multiple drones and three cruise missiles that were fired from Yemen and heading “potentially towards Israel,” a Defense Department spokesman said.

The USS Carney was in the northern Red Sea when it took out the missiles and more than a dozen drones, said Brig. Gen. Patrick Ryder, the Pentagon press secretary.

On Oct. 31, militants believed to be Houthi rebels fired a medium-range ballistic missile from Yemen toward Israel, according to two U.S. officials.

In a statement, the Israel Defense Forces said the missile was intercepted by Israel’s Arrow air defense system, which was jointly developed by Israel and the U.S. The IDF confirmed that a surface-to-surface missile had been fired toward Israeli territory from the direction of the Red Sea, but not did specify whether it had originated in Yemen.