A coalition of Kurdish and Arab forces have captured two villages from armed opposition groups in the northern part of Syria.
The Democratic Forces of Syria (DFS) took control of two villages - Tat Marash and Tanab, in the Azaz region of northern Aleppo - after heavy clashes with rival rebel groups, including al-Nusra Front, according to the Syrian Observatory for Human Rights.
The UK-based monitor reported on Friday unspecified number casualties on both sides.
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The reported advance comes less than a week after DFS seized the strategic Tishreen Dam in northern Syria from the Islamic State of Iraq and the Levant (ISIL), denying the group an important logistics route between Aleppo and its de facto Syrian capital, Raqqa.
DFS, a coalition comprising mainly local Kurds, Arabs and Assyrians, was launched in October, mainly targeting ISIL.
In another development, Syrian government forces claimed to have made gains during an offensive against opposition groups in Quneitra province, near the border of the Israeli-occupied Golan Heights.
Rebel groups said the attacks started on Thursday morning when the Syrian government and pro-regime militias stormed villages in the area.
Syria's conflict, now in its fifth year, has drawn thousands of foreign fighters to the country amid an escalating civil strife.
The Syrian Observatory also reported on Friday that at least 4,600 people, including 1,329 civilians, were killed in Syria's violence in December.
The latest tally comes a day after the monitor said that more than 55,000 people were killed in Syria's conflict in 2015.
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More than 250,000 people are estimated to have been killed in the country since its crisis began in March 2011 with unarmed protests against the regime.
On Thursday, ISIL claimed a pair of bombings that targeted two restaurants in the mostly Kurdish city of Qamishli, situated in northern Syria.
Those attacks left at least 16 people dead, according to Syria state media.
ISIL has suffered some of its worst setbacks in battles with Kurdish fighters in Syria, and has carried out dozens of suicide attacks against the Kurds, including several in Qamishli.