Kurdish forces fighting regime troops in city of Hasakeh, while cooperating in other arenas against ISIS, as convoluted civil war continues.

US soldier directs Kurdish forces in training exercise in Iraq

Kurdish fighters advanced in the flashpoint city of Hasakeh in northeast Syria after a Russian mediation bid failed to halt clashes with pro-regime forces, a monitoring group said Sunday.

The Syrian Observatory for Human Rights and a military source said the Kurds seized territory across several neighborhoods in the city's south in violent clashes on Saturday night.

The Britain-based Observatory said Kurds advanced in Zuhur, while a Kurdish military source told AFP that they pushed forward in Al-Nashwa and Ghweiran.

A local journalist working for AFP said he saw members of the pro-government National Defense Forces militia retreating from Al-Nashwa.

Regime aircraft flew over the city early Sunday morning, most of which is under Kurdish control, but without carrying out any bombing raids, the Observatory said.

In an escalation of Syria's five-year war, regime planes on Wednesday bombarded positions held by US-backed Kurdish forces in the city fighting the Islamic State (ISIS) jihadist group.

The unprecedented strikes prompted the US-led coalition to scramble aircraft to protect its special operations forces helping the Kurdish fighters.

Fighting between a pro-government militia and Kurdish forces since Wednesday has left at least 43 people dead including 27 civilians, among them 11 children, according to the Observatory.

Thousands of civilians have fled the city.

Al-Masdar News, a pro-regime website, said renewed clashes broke out Saturday after the failure of mediation efforts in the neighboring city of Qamishli by a Russian military delegation.

It said the government had rejected a Kurdish demand for pro-regime militiamen to withdraw from Hasakeh, instead proposing that both sides disarm.

A senior regime source told AFP that Russian efforts at mediation continued into Sunday.

The regime and Kurdish forces share a common enemy in ISIS, but there have

been growing tensions between them in Hasakeh.

In the northern province of Aleppo, the scene of heavy clashes all month between government forces and rebels allied with jihadists, 28 civilians were among 38 people killed Saturday in strikes by the regime and its Russian allies, the Observatory said.

More than 290,000 people have lost their lives since Syria's conflict erupted in March 2011, and millions have been forced to flee their homes.