U.S.-backed forces struggled to gain ground against the Daesh (ISIS) in Syria's Raqqa Friday, facing a wave of car bombs and mortars unleashed by the militant group, a monitor said.
The Syrian Democratic Forces penetrated Raqqa's Old City earlier this week after U.S.-led coalition air strikes pierced two holes in its ramparts.
But the SDF and a unit of allied Arab fighters called the Syrian Elite Forces have made little progress inside the historical quarter, the Syrian Observatory for Human Rights monitoring group said.
"Daesh is using car bombs, mortar fire and snipers to wage a counter-offensive inside the Old City," Observatory head Rami Abdel Rahman said.
The Observatory estimates that up to 30 percent of Raqqa has been captured by the U.S.-backed forces since they entered the city on June 6.
Mohammad Khaled Shaker, a spokesman for the Syrian Elite Forces, told AFP there had been no notable advance Friday.
"There are some clashes, but we have not reached the city center yet," he said.
Daesh overran Raqqa in early 2014 and it has since become infamous as the de facto Syrian capital of the group's so-called "caliphate".
An estimated 2,500 militants are left defending Raqqa, according to the U.S.-led coalition.
The global alliance is providing the SDF with air cover, weapons, equipment and special operations forces on the ground as advisers.
The Observatory reported Thursday that the coalition delivered a large shipment of weapons, ammunition and armored vehicles to the SDF via Iraq
