The Islamic State (ISIS) jihadist group launched an assault on the largely Kurdish city of Hasakeh in northeast Syria on Saturday, the Syrian Observatory for Human Rights said.
The attack came a day after Kurdish militia executed 20 civilians accused of supporting the extremists and ISIS on Friday executed 30 civilians, the monitoring group said according to AFP.
"ISIS fighters started an assault on Hasakeh city and reached the city's southern periphery, where they are clashing with pro-regime forces," said Observatory head Rami Abdel Rahman.
He said the pro-government National Defense Forces militia had blocked the ISIS advance on the city's edges and reported heavy shelling.
Syria's official news agency SANA said loyalist forces had "foiled a terrorist attack by ISIS on military points near Hasakeh."
Control of Hasakeh, capital city of the province by the same name, is split between President Bashar al-Assad's regime and Kurdish forces.
Abdel Rahman said at least 10 government loyalists had been killed, but he had no immediate information on ISIS casualties.
The Assyrian Network for Human Rights activist group said ISIS had launched "a new attempt at seizing control of the city" and seized one checkpoint on Hasakeh's southwest edges.
"Hasakeh has been hit by mortar rounds since Saturday morning," and a local church had been damaged, the Network said.
Elsewhere in Hasakeh province, Kurdish militia executed at least 20 civilians Friday, including two children, after accusing them of being ISIS supporters, the Observatory reported.
The Britain-based monitor said Kurdish militia also burned and demolished homes of people it suspected of supporting ISIS near the flashpoint towns of Ras al-Ain and Tal Tamr.
The Kurdish People's Protection Units (YPG) in Hasakeh have been battling ISIS extremists over a series of key towns in the province bordering Turkey.
ISIS on Friday killed 30 civilians trying to escape an advancing jihadist assault, Abdel Rahman said.