A clash between Iranian-backed Houthi fighters who were attacking a commercial freighter and U.S. Navy helicopters responding to the ship’s distress call ended on Sunday morning with the killing of all the crew members on three Houthi boats, the Pentagon said, a sharp escalation of violence at a moment when the White House is considering direct strikes on Iran’s proxies in the Middle East.

It appeared to be the first time that American and allied forces patrolling the Red Sea, a critical waterway for oil and other shipments, have engaged in a deadly firefight with the Houthis since their attacks on ships began in October, following the outbreak of the war between Israel and Hamas. President Biden has said he wants to avoid direct military attacks on the Houthis in Yemen, to avoid escalating a Middle East conflict that is already threatening to spread throughout the region.

But in the fight that broke out on Sunday morning, the Navy forces had little choice, at least according to the account given by United States Central Command.

The Houthis had launched an attack on the freighter, the Maersk Hangzhou, a Singapore-flagged container ship, and were attempting to board it. As the ship’s security forces tried to hold the attackers at bay, helicopters from the U.S.S. Eisenhower carrier group arrived to chase them away and the Houthis opened fire on them.

“The small boats fired upon the U.S. helicopters with crew-served weapons and small arms,” Central Command said in a statement. “The U.S. Navy helicopters returned fire in self-defense, sinking three of the four small boats, and killing the crews.” Central Command did not say how many had been killed, but in a statement later on Sunday the Houthis said that 10 of their fighters were dead.

“The American enemy bears the consequences of this crime,’’ they said in a statement, and “its military movements in the Red Sea to protect Israeli ships won’t prevent” the Houthis from “performing their religious, moral and humanitarian duty in support and aid of those who have been wronged in Palestine and Gaza.”