Tensions have intensified between the United States and Houthi rebels as U.S. military strikes in northern Yemen resulted in the deaths of at least 53 people.

This marks President Donald Trump’s first large-scale military action since returning to office.

Trump attributed the strikes to ongoing Houthi attacks on the Suez Canal that have persisted for 18 months. In a stern warning, he said, “Hell will rain down upon you,” if the attacks do not cease. He also called on Iran to end its support for the rebels, accusing the nation of funding, resourcing, and training the group to target U.S. warships and disrupt global commerce.

An Iranian general denied backing the Houthi rebels and cautioned that Iran would deliver a “tough, decisive and destructive response” to any real threats.

In a speech that aired Sunday night, the rebels’ secretive leader, Abdul-Malik al-Houthi, said: “We will confront escalation with escalation,” according to the Associated Press.

“We will respond to the American enemy in its raids, in its attacks, with missile strikes, by targeting its aircraft carrier, its warships, its ships,” al-Houthi reportedly said. “However, we also still have escalation options. If it continues its aggression, we will move to additional escalation options.”

The Suez Canal, a critical maritime route between Asia and Europe, has seen a 70% drop in freight traffic because of the attacks, leading to increased shipping times and costs.

Secretary of State Marco Rubio said U.S. military action would continue “until the Houthi rebels no longer have the capability to launch their attacks.” He said over the past 18 months the Houthis had attacked the U.S. Navy “directly” 174 times and commercial shipping 145 times using “guided precision anti-ship weaponry,” according to the Associated Press.

“We’re not going to have these people controlling which ships can go through and which ones cannot,” Rubio told CBS on Sunday.

Editor’s note: The National News Desk’s Kristine Frazao contributed to this report.