Syrian regime forces took back several parts of a neighbourhood in the northeastern city of Hasakeh from the Islamic State group on Monday, but heavy clashes continued, a monitor said.
The Syrian Observatory for Human Rights, a Britain-based monitor, said regime forces had seized parts of Al-Nashwa district in southern Hasakeh, which IS fighters entered last Thursday.
But it said clashes were continuing around the neighbourhood with "shelling by both sides and air raids on the area where fighting is taking place".
A security source in Damascus confirmed that fighting was still ongoing in the district.
"In Hasakeh, combat is continuing today, and the army is pursuing Daesh wherever they find them," he said, using the Arabic acronym for IS.
"Daesh is present mostly in parts of the Al-Nashwa district. They have tried to take other areas, but the army has pushed them back," he added.
He said "martyrs are still falling" in Hasakeh but gave no specific toll.
IS launched a new bid to take Hasakeh city, a provincial capital, last week, entering from the south and seizing two neighbourhoods.
The city is divided between the control of regime forces and Kurdish fighters, who have largely kept out of the latest round of fighting.
They have restricted their activity to defending the mostly northern neighbourhoods under their control.
The Observatory said on Monday that IS forces had shelled several Kurdish-controlled districts in the city, but there were no initial reports of casualties.
According to the United Nations, 60,000 people have been displaced by the fighting in Hasakeh, which had a pre-war population of 300,000.
On Sunday, three IS car bombs killed 12 Syrian troops and militiamen in the city, the Observatory said.
Nine IS fighters were also killed in Sunday clashes with the regime, it added.
The army has brought in reinforcements in an attempt to expel the jihadists, as it has done during previous attacks.
IS has repeatedly sought to enter Hasakeh, including last month when it advanced to the southern outskirts before being pushed back in heavy fighting.
IS has captured around 50 percent of Syria's territory since it emerged in the country in 2013.