The strikes also killed at least five civilians, said Rami Abdulrahman, who runs the Britain-based Syrian Observatory for Human Rights.
A third night of U.S.-led air strikes late on Wednesday targeted Islamic State-controlled oil refineries in eastern Syria as the United States and its allies tried to stem a major source of revenue for the al Qaeda offshoot, U.S. officials said.
The strikes hit facilities around al Mayadin, al Hasakah, and Abu Kamal, the U.S. military said.
The initial days of U.S. strikes suggest another aim is to hamper Islamic State`s ability to operate across the Syria-Iraq frontier.
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