A fierce battle between Syrian Kurds and Islamic State jihadists has killed nearly 50 fighters from both sides as the Kurds seized several IS positions, a monitoring group said Thursday.
The Syrian Observatory for Human Rights also reported fighting in eastern Syria between a Sunni tribe and the IS, with members of the tribe tweeting about an "uprising".
Wednesday's fighting in Ain al-Arab (Kobane in Kurdish) killed 14 members of the Kurdish People's Protection Units (YPG) and 35 jihadists.
Dozens of fighters were wounded, said the Observatory.
The Britain-based monitor said it was now "calm" after the fighting in the Ain al-Arab area in the restive northern province of Aleppo on the border with Turkey.
In the battle, Kurdish fighters took several hills which IS jihadists had seized and set up positions.
Earlier in July, hundreds of Kurdish fighters had crossed the Turkey-Syria border into Ain al-Arab, to join the anti-IS fight.
On a separate front, the Shaitat tribe in the eastern province of Deir Ezzor -- most of which is under jihadist control -- also fought back against the IS, the Observatory said.
The fighting erupted after the IS detained three members of the tribe, "violating an agreement" between the two sides, it said.
According to the Observatory, the Shaitat tribe had promised IS it would not oppose it, in exchange for the jihadists not harassing or attacking its members.
The Sunni Shaitat tribe extends across three villages -- Abu Hamam, Kashkiyeh and Ghranij.
Shaitat members posted on Twitter: "Shaitat rises up against the Islamic State."
Five jihadists, including a Belgian, were killed in the fighting, said the Observatory.
IS expelled rivals from oil-rich Deir Ezzor earlier in July, emboldened by its lightning offensive in neighbouring Iraq a month earlier.
Syrian rebels and activists say IS's military capability was boosted by its capture of heavy weapons from Iraqi troops fleeing the onslaught.
IS has been fighting poorly equipped Syrian rebels since January.
Syria's war has killed more than 170,000 people in three years. It began as a peaceful uprising against President Bashar al-Assad but morphed into a complex war after the regime unleashed a brutal crackdown on dissent.