Fresh clashes between Kurdish fighters and jihadists erupted in the majority Kurdish province of Hasakeh in northern Syria early on Friday, a monitoring group said.
At least 12 members of the Islamic State of Iraq and the Levant (ISIS) were killed, said the Syrian Observatory for Human Rights, which added that 22 Kurdish fighters have been killed over the past few days.
Reports of the latest Kurdish-jihadist violence emerged a day after at least 31 civilians, among them five women and four children, were killed in army shelling and an assault in the northwestern province of Idlib.
Meanwhile, Kurdish activists said there was heavy fighting in villages between Cel Agha and Gerke Lage as radical Islamists shelled Ras al-Ain.
"There was fierce shelling of Ras al-Ain at dawn today (Friday)," said Syrian Kurd activist Havidar, who also reported Islamists and Kurds fighting on the edges of the town.
Kurds expelled jihadist groups from Ras al-Ain in mid-July. Clashes have raged ever since in areas that are home to sizeable Kurdish populations.
The fate of some 200 Kurds taken hostage by jihadists on Wednesday remains unknown, the Observatory's Rami Abdel Rahman told AFP.
Elsewhere on Friday, forces loyal to President Bashar al-Assad again shelled the rebel-held area of Jouret al-Shiyah in the central city of Homs, said the Observatory.
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The bombardment comes five days after the key rebel neighbourhood of Khaldiyeh fell out of rebel control and into army hands.
Assad's regime is pressing an offensive aimed at taking back remaining rebel areas in Homs, Syria's third city and dubbed by activists as "the capital of the revolution".
Meanwhile, the air force staged several air strikes on rebel areas across Syria, including two on Al-Harra in the southern province of Daraa, where rebels have made significant progress in recent weeks, said the Observatory.
Friday's violence comes a day after at least 185 people were killed across Syria, the Britain-based watchdog said.
Among them were at least 24 civilians killed in and around the town of Ariha, whose main souk (market) was shelled by regime forces on Thursday, according to the Observatory.
Another seven civilians died in a subsequent army assault on a village near Ariha.
The Observatory also said that at least 43 people were killed in a massive explosion in an ammunitions depot in Homs on Thursday. The blast was apparently triggered by rebel rocket fire.
Most of those killed were members of the regime's paramilitary National Defence Force, said the Observatory, without elaborating.
More than 100,000 people have been killed in Syria's raging war, the United Nations says.