DUBAI, United Arab Emirates (AP) — Ballistic missiles fired by Yemen’s Houthi rebels struck three commercial ships Sunday in the Red Sea, while a U.S. warship shot down three drones in self-defense during the hourslong assault, the U.S. military said. The Iranian-backed Houthis claimed two of the attacks.

The strikes marked an escalation in a series of maritime attacks in the Mideast linked to the Israel-Hamas war, as multiple vessels found themselves in the crosshairs of a single Houthi assault for the first time in the conflict. The U.S. vowed to “consider all appropriate responses” in the wake of the attack, specifically calling out Iran, after tensions have been high for years now over Tehran’s rapidly advancing nuclear program.

“These attacks represent a direct threat to international commerce and maritime security,” the U.S. military’s Central Command said in a statement. “They have jeopardized the lives of international crews representing multiple countries around the world.”

It added: “We also have every reason to believe that these attacks, while launched by the Houthis in Yemen, are fully enabled by Iran.”

The attack began around 9:15 a.m. local time (0615 GMT) in Houthi-controlled Sanaa, Yemen’s capital, Central Command said.

The USS Carney, a Navy destroyer, detected a ballistic missile fired from Houthi-controlled areas of Yemen at the Bahamas-flagged bulk carrier Unity Explorer. The missile hit near the ship, the U.S. said. Shortly afterward, the Carney shot down a drone headed its way, although it’s not clear if the destroyer was the target, Central Command said.

About 30 minutes later, the Unity Explorer was hit by a missile. While responding to its distress call, the Carney shot down another incoming drone. Central Command said the Unity Explorer sustained minor damage from the missile.

Two other commercial ships, the Panamanian-flagged bulk carriers Number 9 and Sophie II, were both struck by missiles. The Number 9 reported some damage but no casualties, and the Sophie II reported no significant damage, Central Command said.

While sailing to assist the Sophie II around 4:30 p.m. local time (1330 GMT), the Carney shot down another drone heading in its direction. The drones did no damage.

The Carney, an Arleigh Burke-class guided-missile destroyer, has shot down multiple rockets the Houthis have fired toward Israel during that nation’s war against Hamas in the Gaza Strip. It hasn’t been damaged in any of the incidents and no injuries have been reported on board. The Defense Department initially described the assault as simply an attack on the Carney before providing more details.

Houthi military spokesman Brig. Gen. Yahya Saree claimed two of Sunday’s attacks, saying the first vessel was hit by a missile and the second by a drone while in the Bab el-Mandeb Strait, which links the Red Sea to the Gulf of Aden. Saree did not mention any U.S. warship being involved.

“The Yemeni armed forces continue to prevent Israeli ships from navigating the Red Sea (and Gulf of Aden) until the Israeli aggression against our steadfast brothers in the Gaza Strip stops,” Saree said. “The Yemeni armed forces renew their warning to all Israeli ships or those associated with Israelis that they will become a legitimate target if they violate what is stated in this statement.”

Saree also identified the first vessel as the Unity Explorer, which is owned by a British firm that includes Dan David Ungar, who lives in Israel, as one of its officers. The Number 9 is linked to Bernhard Schulte Shipmanagement.

The Sophie II’s owner, Kyowa Kisen of Imabari, Japan, told The Associated Press that the ship’s crew were safe and the vessel did not sustain serious damage. Managers for the two other ships could not be immediately reached for comment.

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

Iran has yet to directly address the attacks. However, Iranian Foreign Minister Hossein Amirabdollahian threatened “that if the current situation continues, the region will enter a new phase” over the Israel-Hamas war.

“All parties who are after igniting a war are warned, before it’s too late stop the killing of women and children, of which a new round has started,” Amirabdollahian said.

Iran’s top diplomat described his comments as coming after conversations with “resistance forces” in the region — a description Tehran uses for the Shiite militias it backs, including groups in Iraq, the Houthis and Lebanon’s Hezbollah, as well as the Sunni fighters of Hamas. All have threatened or attacked Israel, Iran’s regional archrival, during the war.

The Houthis have launched a series of attacks on vessels in the Red Sea, as well as launching drones and missiles targeting Israel. Analysts suggest the Houthis hope to shore up waning popular support after years of civil war in Yemen between it and Saudi-backed forces.

The U.S. has stopped short of saying its Navy ships were targeted, but has said Houthi drones have headed toward the ships and have been shot down in self-defense. Washington so far has declined to directly respond to the attacks, as has Israel, whose military continues to try to describe the ships as not having links to their country.

Global shipping had increasingly been targeted as the Israel-Hamas war threatens to become a wider regional conflict — even as a truce briefly halted fighting and Hamas exchanged hostages for Palestinian prisoners held by Israel. However, the collapse of the truce and the resumption of punishing Israeli airstrikes on Gaza and a ground offensive there had raised the risk of more seaborne attacks.

In November, the Houthis seized a vehicle transport ship also linked to Israel in the Red Sea off Yemen. The rebels still hold the vessel near the port city of Hodeida. Missiles also landed near another U.S. warship last week after it assisted a vessel linked to Israel that had briefly been seized by gunmen. Separately, a container ship owned by an Israeli billionaire recently came under attack by a suspected Iranian drone in the Indian Ocean.

The Houthis had not directly targeted the Americans for some time, further raising the stakes in the growing maritime conflict. In 2016, the U.S. launched Tomahawk cruise missiles that destroyed three coastal radar sites in Houthi-controlled territory to retaliate for missiles being fired at U.S. Navy ships at the time.