The Syrian army said it had retaken a swathe of territory from Islamic State in southern Syria on Thursday in a rapid advance near areas held by U.S.-backed Syrian rebels at the border with Jordan and Iraq. Tensions flared in the southern region last week when the U.S.-led coalition mounted an air strike against pro-government forces that U.S. officials said posed a threat to U.S. and U.S.-backed Syrian fighters in the area. Washington described the forces as Iranian-directed. The Syrian army on Thursday declared the capture of areas to the south of Palmyra and to the east of Qaryatayn in southeastern Homs province. An official with one of the Free Syrian Army (FSA) rebel groups operating in southern Syria told Reuters that government forces appeared to be trying to preempt any rebel move toward Deir al-Zor, another priority target for the government.