Syrian Kurdish fighters in the northeast expelled jihadists from a checkpoint on Saturday and seized their weapons and ammunition, the Syrian Observatory for Human Rights reported.
The advance comes just days after Kurdish fighters loyal to the Democratic Union Party (PYD) expelled jihadists allied to Al-Nusra Front and the Islamic State of Iraq and the Levant (ISIS) from the strategic Kurdish town of Ras al-Ain.
In five days of fighting, at least 35 jihadists and 19 Kurdish fighters have been killed, the Britain-based Observatory said.
"Clashes raged during the night from Friday to Saturday, pitting (Kurdish fighters) against Al-Nusra Front, ISIS and other (rebel) groups... near the villages of Tal Alu, Karhuk and Ali Agha," said the group.
The clashes "ended at 8:00 am (0500 GMT), when the Kurdish popular committees seized control of a... (key) checkpoint" there, said the group.
The Kurdish fighters then seized ammunition, light weapons, a vehicle mounted with a heavy machinegun and a mortar from the jihadists, the Observatory added.
The PYD has said that Syria's Kurds are planning to create a temporary autonomous government to administer their regions in the north.
Kurdish regions have been run by local Kurdish councils since President Bashar al-Assad's forces withdrew from the areas in mid-2012.
Since then, the Kurds have walked a fine line, trying to avoid antagonising either the regime or the rebels, and focusing on maintaining security while strengthening control over their own affairs.
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Kurds represent about 15 percent of the Syrian population.
In the northern province of Raqa, Al-Nusra Front fighters detained five Kurdish civilians late on Friday in the town of Tal Abyad to the north, said the Observatory.
Anti-Assad activists in Raqa have staged frequent protests in recent weeks over abuses by Al-Nusra and other jihadists.
Meanwhile in northwest Syria, the air force kept up a fierce campaign against the town of Saraqeb and staged some 12 air strikes there on Saturday, killing two children, three women and a man.
Air raids also targeted areas where the rebels were reportedly advancing in Aleppo province in northern Syria, the Observatory said.
The raids came as rebels advanced on Khan al-Assal, the only town in the west of Aleppo province still under regime control.
Twelve soldiers were killed there in fighting Saturday, the Observatory said.
In central Damascus, an explosive device planted in the Emara neighbourhood killed one person, it said, and several mortar rounds hit the Abasiyeen district in the northeast.
Saturday's violence comes a day after at least 95 people were killed across Syria, it added.
More than 100,000 people, most of them civilians, have died in Syria's 28-month war, the group says.