AMMAN (Reuters) -The U.S. military on Thursday hit several targets in the Syrian city of Mayadin in parts of Deir al Zor province under government control, in the third day of skirmishes with Iran-backed groups, local military sources said. They said at least three members of an Iran-aligned militia were killed when they were targeted by a U.S. helicopter as they were about to prepare a rocket launcher in the town which lies along the western bank of the Euphrates River. Iranian militias have a strong presence in the town and have long targeted the nearby Al Omar oil field on the eastern bank of the Euphrates where the U.S. coalition have their biggest base in Syria. The base also known as Green Village was last night targeted in a second consecutive day of violence between the U.S. military and Iran-backed militants. A U.S. official, speaking on the condition of anonymity, said the United States carried out retaliatory strikes on Thursday in the area. In the past 24 hours, the U.S. military said, four militants have been killed and seven rocket launchers have been destroyed. The latest flare-up of violence which underscored soaring military tensions even amid diplomatic efforts between Tehran and the West to try to save Iran's 2015 nuclear deal with major powers. The Pentagon has said a total of three service members suffered minor injuries as a result of the back-and-forth on Wednesday. Wednesday's strikes came a day after President Joe Biden authorized U.S. air strikes in Syria on an ammunition depot and other facilities used by groups affiliated with Iran's elite Revolutionary Guards Corps (IRGC). (Reporting by Suleiman Al-Khalidi. Additional reporting by Idrees Ali and Phil Stewart; editing by Jonathan Oatis and Alistair Bell)