BEIRUT (Reuters) - Syrian government forces and their allies advanced against Islamic State militants in countryside east of Raqqa on Thursday, war monitors reported.
The advance, to within four km (2.5 miles) of the town of Maadan, crossed the provincial boundary between Raqqa and Deir al-Zor for the first time from the west, the Britain-based Syrian Observatory for Human Rights said.
The monitoring group has reported recent advances in the area by the Syrian army, nearing territory controlled by U.S.-backed forces who are separately fighting Islamic State in the jihadists' stronghold of Raqqa city.
Incidents involving the U.S.-backed forces and pro-Damascus forces last month caused tension between Washington and Syrian government ally Moscow.
Islamic State is losing ground fast in Syria to separate campaigns waged by the Russian-backed Syrian government on the one hand, and U.S.-backed regional Kurdish forces and their allies on the other.
Deir al-Zor province, which borders Iraq to the east, is almost entirely under Islamic State control. The Syrian government has clung to a pocket of territory in Deir al-Zor city, the provincial capital, and at a nearby air base.
(Reporting by John Davison; editing by Mark Heinrich)