The clashes broke out between the so-called Islamic State of Iraq and the Levant (ISIL) and the al-Nusra Front terrorist group on Saturday in the strategic town of Markada, in the south of Hasakah province, the London-based pro-opposition group called Syrian Observatory for Human Rights said on Sunday.
According to the group, armed ISIL insurgents overran the town held by the rival al-Qaeda-linked group.
Markada is located on the border with Iraq, where the ISIL militants have been increasingly active over the past months.
The extremist militants have been fighting the al-Nusra Front since January across western, northern and eastern Syria.
On Saturday, reports from Syria said ISIL’s military commander Omar Farough al-Turki was killed by al-Nusra militants in Hasakah.
The foreign-backed Takfiri groups had reportedly engaged in heavy fighting earlier in the day in the oil-rich province of Deir Ezzor in eastern Syria.
In February, Syrian opposition sources said infighting among extremist militants operating in Syria had left around 3,300 casualties since January. Similar clashes claimed over 1,000 lives in January alone.
Syria has been gripped by deadly violence since March 2011. Damascus says the West and its regional allies have been fuelling the unrest by providing militants with money and weapons.
According to the United Nations, more than 100,000 people have been killed in the ongoing militancy in Syria and a total of 7.8 million others have been displaced due to the violence. Some reports, however, claim that the death toll from the conflict exceeds 140,000.
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