The United States military announced on Tuesday that it launched airstrikes this week in northeastern Syria. The strikes were targeted at militant groups linked to Iran’s Islamic Revolutionary Guards Corps. The U.S. carried out additional airstrikes on Shia militants in Syria on Thursday.

The Pentagon said a total of four Iranian-backed militants had been killed in the series of U.S. strikes, reports CNN. In response, the militants launched rocket attacks that wounded three U.S. servicemen.