DUBAI, United Arab Emirates (AP) — Merchant ships were attacked by drones and missiles in the Red Sea on Sunday and a U.S. warship opened fire there in self-defense as part of an hours-long attack by Yemen’s Houthi rebels, officials said.

The attack may have represented a significant escalation in a series of naval attacks in the Middle East linked to the Israel-Hamas war, as multiple ships found themselves in the crosshairs of a single Houthi attack for the first time in that conflict.

“We are aware of reports of attacks on the USS Carney and merchant vessels in the Red Sea and will provide information as it becomes available,” the Defense Department told The Associated Press.

The Carney is an Arleigh Burke-class guided-missile destroyer that has already shot down several missiles that the Houthis have fired at Israel so far in the war. It was not damaged in the attack and no injuries were reported on board, said a U.S. official, speaking on condition of anonymity to discuss early details of a military operation.

The Carney responded after learning from the Bahamian-flagged bulk carrier Unity Explorer that it was under attack by missile fire, the official said. The Carney shot down two drones during the attack, one in self-defense and another after checking on the Unity Explorer, the official said.

Reviews were still being made on Unity Explorer.

The British military had previously said there had been a suspected drone strike and explosions in the Red Sea, without elaborating.

The Defense Ministry did not say where it believed the fire came from. Houthi military spokesman Brig. Gen. Yahya Saree claimed the first ship was hit by a missile and the second by a drone in the Bab el-Mandeb Strait, which connects the Red Sea with the Gulf of Aden.

Saree did not mention that a US warship was involved in the attack.

“Yemeni forces continue to prevent Israeli ships from entering the Red Sea (and the Gulf of Aden) until Israeli aggression against our steadfast brothers in the Gaza Strip ceases,” Saree said. “The Yemeni Armed Forces reiterate their warning to all Israeli vessels or those associated with Israelis that they will become a legitimate target if they violate the statements of this statement.”

Saree also identified the first ship as the Unity Explorer, owned by a British company whose officers include Israel resident Dan David Ungar. The second was a Panamanian-flagged container ship named Number 9, affiliated with Bernhard Schulte Shipmanagement. The managers of the two ships could not immediately be reached for comment.

Israeli media identified Ungar as the son of Israeli shipping billionaire Abraham “Rami” Ungar.

The Houthis have launched a series of attacks on ships in the Red Sea and fired drones and missiles at Israel during the war.

Another U.S. official, who spoke on condition of anonymity to discuss intelligence matters, said the attack began around 10 a.m. in Sanaa, Yemen, and lasted up to five hours.

Global shipping has come under increasing scrutiny as the war between Israel and Hamas threatens to become a larger regional conflict – even as a ceasefire briefly halted fighting and Hamas exchanged hostages for Palestinian prisoners held by Israel. However, the collapse of the ceasefire and the resumption of punishing Israeli air strikes and its ground offensive there had increased the risk of a resumption of naval attacks.

At the beginning of November, the Houthis seized a vehicle transport ship that was also linked to Israel in the Red Sea off Yemen. The rebels are still holding the ship near the port city of Hodeida. Missiles also landed near another U.S. warship last week after it aided an Israeli-linked ship that was briefly hijacked by gunmen.

However, the Houthis had not directly targeted the Americans for some time, further increasing the risk of the worsening maritime conflict. In 2016, the US launched Tomahawk cruise missiles that destroyed three coastal radar sites in Houthi-controlled territory in retaliation for missiles fired at US Navy ships at the time.

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Associated Press writers Tara Copp in Dallas, Lolita C. Baldor in Washington and Dana Beltaji contributed.