The U.S. began conducting airstrikes in Iraq and Syria on Friday against Iran's Islamic Revolutionary Guard Corps (IRGC) and affiliated groups, the U.S. Central Command said, in what the Biden administration has called a "multi-tiered" response to a deadly drone attack that killed three American soldiers last Sunday.

U.S. forces struck more than 85 targets associated with the IRGC's elite Quds Force and affiliated militias with numerous aircraft, including long-range bombers flown from the United States, U.S. Central Command said in a social media post. The airstrikes used more than 125 precision munitions against command and intelligence centers, storage facilities for rockets, missiles and unmanned aerial vehicles, and logistics and munition supply chain facilities of "militia groups and their IRGC sponsors who facilitated attacks against U.S. and coalition forces," Central Command added.

"Our response began today. It will continue at times and places of our choosing," President Biden said in a statement on Friday. "The United States does not seek conflict in the Middle East or anywhere else in the world. But let all those who might seek to do us harm know this: If you harm an American, we will respond."

Mr. Biden told reporters Monday he had decided on a response, and Defense Secretary Lloyd Austin said Thursday it was time to take away "even more capability than we've taken in the past." 

U.S. officials told CBS News earlier this week there were plans for a series of strikes against targets that include facilities and personnel associated with Iran's Islamic Revolutionary Guard Corps in Iraq and Syria.

The administration blamed the drone strike on the group Islamic Resistance of Iraq, a group of militias backed by Iran. Austin on Thursday said it's unclear if Iran knew about the drone attack ahead of time, but without Iran, these attacks wouldn't take place. 

"How much Iran knew or didn't know, we don't know — it really doesn't matter because Iran sponsors these groups, it funds these groups, and in some cases, it trains these groups on advanced conventional weapons," Austin said. 

On Friday, the USS Carney engaged and shot down "one unmanned aerial vehicle over the Gulf of Aden", CENTCOM said in a statement. Later in the day, U.S. Central Command forces conducted strikes against four Houthi UAVs that were prepared to launch, and that evening local time the Dwight D. Eisenhower Carrier Strike Group engaged and shot down seven UAVs over the Red Sea, the statement said. No injuries were reported.

Iranian-backed groups have attacked U.S. forces in Iraq and Syria over 160 times since October, but until Sunday's attack in Jordan, no U.S. service members had been killed. 

In:
• Iraq
• Iran

Eleanor Watson

Eleanor Watson is a CBS News reporter covering the Pentagon.

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