A U.S. contractor was killed and five U.S. service members and one other U.S. contractor were wounded when a suspected Iranian drone struck a facility on a coalition base in northeast Syria on Thursday, the Pentagon said. In a statement, Defense Secretary Lloyd Austin said U.S. Central Command forces retaliated with "precision airstrikes" against facilities in eastern Syria used by groups affiliated with Iran's Revolutionary Guard. There were unconfirmed reports Friday morning that a new missile strike had targeted a U.S. base in the same region, near the Al-Omar oil field in northeast Syria. The Reuters news agency and local media, including a pro-Iran outlet based in Lebanon, reported the strike. Photos and reports on social media suggested at least one missile had missed the intended target and hit homes in the region instead. There was no immediate confirmation from U.S. officials about a new strike targeting American forces or their allies. The Defense Department said the intelligence community had determined the unmanned aerial vehicle used in the Thursday attack was of Iranian origin. Two of the wounded U.S. service members were treated on site, while three others and the injured contractor were transported to medical facilities in Iraq, the Pentagon said.   The Syrian Observatory for Human Rights, an opposition war monitor, said the American strikes killed six Iranian-backed fighters at an arms depot in the eastern city of Deir el-Zour. The Observatory, which relies on a network of local contacts in Syria, said the U.S. also bombed an outpost near the town of Mayadeen, killing another two fighters.

A separate American strike hit a military post near the town of Boukamal, along the border with Iraq, on Thursday the Observatory said. CBS News hasn't been able to confirm the report.

"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 Iran's Revolutionary Guard, Austin said, adding that he authorized the retaliatory strikes at the direction of President 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 United States took proportionate and deliberate action intended to limit the risk of escalation and minimize casualties," Austin said. The Reuters news agency said that, in testimony to the House Armed Services Committee on Thursday, Kurilla said Iran's drone fleet had become "the largest and most capable unmanned aerial vehicle force in the region." Overnight, videos on social media purported to show explosions in Syria's Deir el-Zour, 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 .