The Britain-based Syrian Observatory for Human Rights said the early Friday counterattack by IS short-circuited a government advance on Maadan, which brought them within only a few kilometers (miles) in recent days.
The Russia-backed government forces have been on a multi-pronged offensive, moving toward the IS-held territories in Deir el-Zour province in the east from northern, central and southern Syria. On Friday, the Russian military said its air force is now focusing on supporting the Syrian army's offensive in Deir el-Zour. Syrian government forces control around half the city and a nearby air base, both of which are besieged by the IS militants.
Col. Gen. Sergei Rudskoi of the military's General Staff said the Russian two-year campaign backing the Syrian government has allowed President Bashar Assad's forces to quadruple the territory under their control.
At a news conference in Moscow, he said the area under Syrian government control has increased from 19,000 to 78,000 square kilometers (7,335 to 30,115 square miles) since Russia launched its air campaign in September 2015. Russian pilots have flown more than 28,000 missions since the campaign's launch, he said.
Rudskoi said Syrian government troops are advancing from three directions to encircle Deir el-Zour. "Breaking the blockade of the city will mark the defeat of the most capable part of the IS in Syria," he said.
The IS attack Friday set the government back about 30 kilometers (19 miles) to the west of Maadan and allowed the militants to recapture a number of villages in the areas they lost to advancing government troops last month. Maadan lies halfway between Raqqa city and Deir el-Zour city, which is divided between government- and IS-controlled areas.
The Observatory called the IS attack its biggest in southeastern Raqqa. It said at least 34 Syrian soldiers and 12 militants were killed. IS media channels posted pictures of the attacked Syrian army convoy and bodies of over a dozen soldiers. Maadan lies along the southern banks of the Euphrates River and is 60 kilometers (37 miles) east of the city of Raqqa, where the U.S-backed Syrian opposition forces are separately battling IS.
The militants have unsuccessfully tried to push back against government advances in central Syrian town of Akerbat. Russian officials said Syrian troops have encircled IS militants in the town and Gen. Sergei Surovikin, the head of Russia's military in Syria, said controlling Akerbat would allow the Syrian government to take full control of the oil and gas fields north of Palmyra.
Associated Press writer Vladimir Isachenkov in Moscow contributed to this report.