(Adds fresh strikes)
BEIRUT, Sept 25 (Reuters) - At least 14 Islamic State fighters were killed in air strikes by U.S.-led forces overnight in northeast Syria, a group monitoring the war said on Thursday, and the Syrian air force bombed rebel areas in the west of the country.
The U.S-led strikes killed at least five civilians, said Rami Abdulrahman, who runs the Britain-based Syrian Observatory for Human Rights.
Syrian forces carried out air raids using barrel bombs in the west of the country, in areas where rebel forces opposed to Islamic State operate. Syrian state TV said the army had also recaptured an area northeast of Damascus.
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 Albu 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.
The Observatory said Syria's air force also dropped barrel bombs in the countryside north of Homs city. Further north Syrian helicopters used barrel bombs on a village outside Hama and warplanes bombed areas in the northern countryside of Latakia province, the Observatory said. (Reporting by Tom Perry; Writing by Sylvia Westall; Editing by Dominic Evans)