US warplanes struck a weapons storage facility used by Iran and its proxies in eastern Syria shortly after Tehran-backed Houthi forces in Yemen shot down an American MQ-9 Reaper drone.

In a statement, Defense Secretary Lloyd Austin said the strike was in response to more than three dozen attacks on American military sites across Iraq and Syria since Oct. 17.

“The President has no higher priority than the safety of U.S. personnel, and he directed today’s action to make clear that the United States will defend itself, its personnel, and its interests,” Austin said.

“The United States is fully prepared to take further necessary measures to protect our people and our facilities. We urge against any escalation. U.S. personnel will continue to conduct counter-ISIS missions in Iraq and Syria.”