Fresh battles have broken out in strategic, majority Kurdish areas in Syria, as jihadists and the main Kurdish party fight each other for control.
In the northeastern province of Hasakeh, "clashes broke out at dawn pitting the Committees for the Protection of the Kurdish People (YPG) against the Islamic State of Iraq and the Levant (ISIS), Al-Nusra Front and other battalions," said the Syrian Observatory for Human Rights on Tuesday.
The fighting hit Dardara, Hmeid and Jafa villages, and others surrounding the strategic town of Ras al-Ain, near the Turkish border, the watchdog said.
The fighting comes days after jihadists linked to Al-Qaeda pressed a fresh offensive to take control of majority Kurdish areas.
Violence has been so fierce in recent days that some 30,000 Syrians, mostly Kurds, have fled to neighbouring Iraq, the UN said on Monday.
The massive exodus late last week appeared to be the biggest since around 9,000 Syrians crossed into Turkey in November.
"There is a war for territory, control and oil," said Havidar, a Kurdish activist from Ras al-Ain, who added that the town is important because it is a key gateway from Turkey into Syria.
Other flashpoints are home to oil and agricultural resources that both the YPG and the jihadists want to control, he told AFP.
The Kurdish Democratic Union Party, the largest in the area and the group that dominates the YPG, has announced plans for autonomy in Kurdish areas.
Elsewhere in Syria, canon fire by troops loyal to President Bashar al-Assad against the rebel-held Tariq al-Bab neighbourhood of the northern city of Aleppo killed four people, said the Observatory.
A projectile "launched by regime troops against a popular market in the Tariq al-Bab area killed four people, including a child, and wounded seven others," it said.
Syria's war, which the UN says has claimed more than 100,000 lives in 29 months, has morphed from a protest movement demanding Assad's fall into a complex civil war.
