Jihadists gained ground Friday from rebels in Syria's last major opposition bastion after four days of fighting that has killed more than 100 fighters, a war monitor said.
Hayat Tahrir al-Sham, a jihadist-led alliance, seized more than 20 villages from rival rebels in the northern province of Aleppo, the Syrian Observatory for Human Rights said.
"HTS was able to take control of areas previously held by Nureddine al-Zinki in the west of the Aleppo countryside," the Britain-based monitor said.
Those areas lie in the northeast of Syria's last major rebel bastion, which includes a large part of Idlib province as well as adjacent parts of Aleppo and Hama provinces.
The clashes broke out after HTS, which is led by Syria's former Al-Qaeda affiliate, on Monday accused Nureddine al-Zinki of killing five of its fighters.
Fighting flared on Tuesday in the northern province of Aleppo before expanding to the neighbouring provinces of Idlib and Hama in the following days.
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Friday's fighting brought the death toll to 58 HTS fighters, 56 rebels, and eight civilians in four days, the Observatory said.
Over the past two years, HTS has regularly fought a rival alliance of rebels called the National Liberation Front, which includes Nureddine al-Zinki, for territory in and around Idlib province.
Since September, a buffer zone deal between rebel backer Turkey and government ally Russia has shielded the Idlib region from a massive regime offensive.
Sparked by the brutal repression of anti-government protests in 2011, Syria's civil war has killed more than 360,000 people and displaced millions.