The U.S. launched strikes on Iranian-linked targets in Syria on Thursday in retaliation for a series of drone attacks on American military bases in the region, Defense Secretary Lloyd Austin said.

“Today, at President Biden’s direction,” Austin said, “U.S. military forces conducted self-defense strikes on two facilities in eastern Syria used by Iran’s Islamic Revolutionary Guard Corps (IRGC) and affiliated groups. These precision self-defense strikes are a response to a series of ongoing and mostly unsuccessful attacks against U.S. personnel in Iraq and Syria by Iranian-backed militia groups that began on October 17.”

The U.S. military action comes amid rising tensions in the region over the conflict in Israel. Austin called the attacks “separate and distinct from the ongoing conflict between Israel and Hamas” and said they don’t represent a shift in the U.S. approach to the conflict.

From Oct. 17 to Tuesday, U.S. and coalition forces were attacked at least 10 separate times in Iraq and three times in Syria by a mix of drones and rockets, the Defense Department has said. On Oct. 18, at least two one-way attack drones targeted al-Tanf military base in southern Syria, U.S. Central Command said. On the same day, there were two separate drone attacks against U.S. and coalition forces stationed at al-Asad base in western Iraq.

Austin said, “As a result of these attacks, one U.S. citizen contractor died from a cardiac incident while sheltering in place; 21 U.S. personnel suffered from minor injuries.” All those injured have since returned to duty, he said.

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“The President has no higher priority than the safety of U.S. personnel,” Austin said, “and he directed today’s action to make clear that the United States will not tolerate such attacks and will defend itself, its personnel, and its interests.”

He said: “The United States does not seek conflict and has no intention nor desire to engage in further hostilities, but these Iranian-backed attacks against U.S. forces are unacceptable and must stop. Iran wants to hide its hand and deny its role in these attacks against our forces. We will not let them.”

Brig. Gen. Pat Ryder, the Pentagon press secretary, said Tuesday the groups conducting the attacks are supported by Iran and its Islamic Revolutionary Guard Corps.

“We always reserve the right to defend ourselves, and we will never hesitate to take action when needed to protect our forces and our interests overseas,” he added.