The Syrian Observatory for Human Rights also reported that 11 civilians were killed in a government air raid on the rebel-held town of Irbin northeast of Damascus.
The clashes that erupted on Saturday as the IS launched an offensive aimed at seizing Tal Tamr in Hasakeh province from Kurdish forces have killed 40 fighters on both sides, it said.
"Fierce battles broke out during the past 24 hours around Tal Tamr... that killed 40 fighters," said Observatory director Rami Abdel Rahman.
He said the fighting erupted when IS advanced close to the town, but the Kurds called in reinforcements and were able to repel the jihadists.
IS has been trying to capture Tal Tamr because of its strategic location.
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Taking it would allow IS to dominate a key road between the eastern part of Hasakeh and the town of the same name that are held by the Kurds, and also gain access to the Iraqi border and the jihadist bastion in Mosul beyond.
Sunday's raid on Irbin near Damascus during which missiles were fired at the town also wounded 50 people, some of them critically, the Observatory said.
It also reported several civilians wounded in regime-held areas of Damascus by rebel rocket fire, without giving a precise toll.
Elsewhere, clashes were still under way around the Aleppo province villages of Handarat and Bashkoy between regime forces and fighters from the Al-Qaeda affiliate, Al-Nusra Front.
The Observatory said that a child and a local Nusra commander were killed in the fighting.
A military source told AFP that loyalist forces had launched an overnight offensive on rebel positions in Handarat after failing to recapture it last month.