WASHINGTON (AP) — Four Iranian-backed militia members were killed in U.S. strikes in Syria on Wednesday in response to attacks by the group in recent weeks, the U.S. military said Thursday.

In a statement, U.S. Central Command said U.S. forces also destroyed seven enemy rocket launchers on Wednesday hours after militia fighters fired rockets at two U.S. military installations in northeast Syria. Central Command provided additional details about the strikes on Thursday, saying they were done with Apache helicopters, AC-130 gunships and M777 Howitzers.

The latest spike in attacks came after militias backed by Iran’s paramilitary Revolutionary Guard targeted U.S. troops on Aug. 15 at the al-Tanf Garrison in the south. There were no casualties or damage in that attack. But, in response, the U.S. struck bunkers and facilities used by the militias.

At the Pentagon on Thursday, Air Force Brig. Gen. Patrick Ryder said it would be premature to say if these strikes represent a broader escalation of violence in Syria.

“Certainly time will tell,” said Ryder, the Pentagon’s press secretary. “Based on the strikes that we have taken, we’ve sent a very loud and clear message, and a proportional message, that any threat against our forces who are operating in Syria or anywhere will not be tolerated. My hope would be that these groups would have received the message loud and clear and that we will not see similar behavior in future.”

President Joe Biden informed Congress of his decision to approve the initial U.S. strikes on the bunker facility, saying the goal was to disrupt the ongoing series of attacks and “to deter the Islamic Republic of Iran and Iran-backed militia groups from conducting or supporting further attacks on United States personnel and facilities.”

The opposition war monitor the Syrian Observatory for Human Rights said that the U.S. airstrikes on the bunkers targeted the Ayash Camp run by the Fatimiyoun group made up of Shiite fighters from Afghanistan and that at least six Syrian and foreign militants were killed.

Within hours after the U.S. strikes, militia rocket attacks hit Green Village and the Conoco gas field in Deir el-Zour, where U.S. troops are stationed. According to U.S. Central Command, at least three servicemembers were treated or evaluated for minor injuries. U.S. forces retaliated by targeting the rocket launchers.

“We will respond appropriately and proportionally to attacks on our servicemembers,” said Gen. Erik Kurilla, who heads U.S. Central Command. “No group will strike at our troops with impunity.”

Deir el-Zour is a strategic province that borders Iraq and contains oil fields. Iran-backed militia groups and Syrian forces control the area and had often been the target of Israeli war planes in previous strikes.

Iran Foreign Ministry spokesman Nasser Kanaani has denied that Iran had any link to those targeted. Iran routinely denies arming militia groups that target U.S. forces in the region, despite weaponry linking back to them.

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