(NewsNation) — A U.S. contractor was killed and five service members and one other contractor injured by a drone strike on a coalition base Thursday in northeast Syria, the Defense Department said.

Defense Secretary Lloyd Austin ordered retaliatory “precision airstrikes” against facilities used by groups affiliated with Iran’s Islamic Revolutionary Guards Corps, the Pentagon said in a statement. The drone that carried out the strike on U.S. personnel is believed to be of Iranian origin.

“The airstrikes were conducted in response to today’s attack, as well as a series of recent attacks against Coalition forces in Syria by groups affiliated with the IRGC,” Austin said in the statement.

Two of the wounded service members were treated on-site, while three additional service members and the U.S. contractor were evacuated to medical facilities in Iraq, the Pentagon said.

Overnight, videos on social media purported to show explosions in Syria’s Deir Ez-Zor, a strategic province that borders Iraq and contains oil fields.

Iran-backed militia groups and Syrian forces control the area, which also has seen suspected airstrikes by Israel in recent months allegedly targeting Iranian supply routes.

The Pentagon said the strikes were authorized by President Joe Biden.

“As President Biden has made clear, we will take all necessary measures to defend our people and will always respond at a time and place of our choosing,” Austin said. “No group will strike our troops with impunity.”

The Associated Press contributed to this report.