(NewsNation) — The U.S. military reports three commercial ships in the Red Sea were struck by ballistic missiles fired from Houthi-controlled Yemen, and a U.S. warship shot down three drones in self-defense during the hourslong assault. 

Iranian-backed Houthi rebels claimed responsibility. 

Former U.S. National Security Adviser Ambassador John Bolton noted there have been several launches of drones and missiles by the Houthis north up the Red Sea, but it’s unclear whether they were aimed at commercial vessels, U.S. ships or intended for Israel or something nearby.

“To be clear, the Houthis would have no capability, whatever, in this regard, if it weren’t for Iran. Houthis have used these weapons supplied by Iran, previously attacking civilian targets in Saudi Arabia and the United Arab Emirates,” he said. “There’s no doubt really who has the right to tell them to press the button; it is Iran.”

The attacks 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. U.S. Central Command says the attacks represent a direct threat to international commerce and maritime security.

Bolton expressed concern, noting the danger in the Red Sea due to its crucial role in the American Navy’s route between the Mediterranean and Arabian Seas.

“It’s also hugely important for international commerce — ships that go through the Suez Canal have to exit at the southern end of the Red Sea into the Arabian Sea through a very narrow strait. This ability of the Houthis to attack these ships, which amount maybe to 10% of international commerce, like 20,000 ships or more, go through the Suez Canal every year is a very significant choke point,” he explained.

He added: “This activity should be of concern to the U.S. I wouldn’t call it an escalation because I think we’re in an escalated war already; I don’t think this is just a Hamas-Israel conflict.”

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.

The Associated Press contributed to this report.