BEIRUT: Fighting between the Syrian army and Kurdish forces intensified late on Friday and into Saturday, creating the risk of yet another front opening in the multi-sided civil war.
The two sides have mostly avoided confrontation during the five-year conflict, with the government focusing its efforts against Arab rebels in the west, and the Kurds mainly fighting IS in northern Syria.
In an indication of their reluctance to escalate further, pro-government media said on Saturday they had held preliminary peace talks.
After the fighting broke out this week, government warplanes bombed Kurdish-held areas of Hasaka, one of two cities in the largely Kurdish-held northeast where the government has maintained enclaves.
Fighting there could complicate the battle against IS because of the Kurds' pivotal role in the US-backed Syrian Democratic Forces' (SDF) fight against the group.
Meanwhile, Turkey will take a more active role in addressing the conflict in Syria in the next six months to prevent the war-torn country being divided along ethnic lines, Turkish Prime Minister Binali Yildirim said on Saturday.
Yildirim also told a group of reporters in Istanbul that while Syrian President Bashar al-Assad could have a role in the interim leadership, he must play no part in its future.
"Turkey we will be more active in the Syria issue in the coming six months as a regional player.
This means to not allow Syria to be divided on any ethnic base, for Turkey this is crucial," Yildirim said.
On Friday, warplanes from the US-led coalition flew what the Pentagon called protective patrols around Hasaka to prevent Syrian jets from targeting US special forces, who are operating on the ground with the SDF, the first sorties of their kind in the war.
Ground fighting intensified late on Friday when Kurdish YPG fighters battled Syrian forces, whose air force flew sorties over the city, Kurds and monitors said.
"The clashes continue in areas inside the city today.
There were military operations," a Kurdish official said.
Many inhabitants of Kurdish areas fled on Friday and at least 41 people have been killed, the Syrian Observatory for Human Rights, a UK-based war monitoring group, said.
"There are efforts to cool things between the army and the Asayish (YPG-affiliated forces), and a first meeting was held aimed at a ceasefire," Sham FM, a pro-government radio station, reported.
As well as complicating the war against IS, fighting in Hasaka could create problems for the government's campaign in the city of Aleppo, where Kurdish forces have been accused of coordinating with the Syrian army against rebels backed by Turkey.
The YPG, or People's Protection Units, have close ties with the Kurdistan Workers Party (PKK) in Turkey, against which Ankara has waged a three-decade counter insurgency.
Turkey fears the Kurds' drive against IS State is partly aimed at carving out a Kurdish region along its own southern border.
Local fighters backed by the SDF, of which the YPG militia form an integral part, said on Saturday they would not advance further north - towards the Turkish border - having secured the city of Manbij, 250 km (155 miles) west of Hasaka, from IS, an announcement that may have been aimed at assuaging Turkish fears.
Syria's army has blamed the YPG for the Hasaka fighting and described it as a branch of the PKK, a characterisation the group rejected on Saturday.
In Aleppo, fighting continued near the mouth of a corridor that rebels opened this month into besieged areas they control.
Jakob Kern, the Syria director of the United Nations' World Food Programme, said opposition-held areas had been inaccessible for weeks and food was running perilously short.
"In the east of Aleppo, the food will last a maximum of two weeks, probably until the end of August," Swiss newspaper Tages-Anzeiger quoted him as saying on Saturday.
Russia, the main military backer of Syrian President Bashar Al Assad, said on Thursday it was willing to support weekly 48-hour ceasefires to allow aid to reach besieged areas.