The so-called Islamic State of Iraq and the Levant (ISIL) terrorist group withdrew from the eastern Syrian province of Deir Ezzor on Monday after a three-day battle with Islamist rebels.

The so-called Islamic State of Iraq and the Levant (ISIL) terrorist group withdrew from the eastern Syrian province of Deir Ezzor on Monday after a three-day battle with Islamist rebels, a monitor said.

The UK-based Syrian Observatory for Human Rights said ISIL withdrew from the province, which borders Iraq, after fighting a coalition of opposition brigades including Al-Qaeda's Syria affiliate Al-Nusra Front terrorist group.

ISIL is facing a widespread backlash from an array of opposition brigades over distributing control.

Though it grew from Al-Qaeda's onetime Iraqi affiliate, Al-Qaeda chief Ayman al-Zawahiri has distanced his organization from ISIL and ordered it to return to Iraq.

The Observatory said it joined around 10 other brigades in the fight against the Takfiri group in Deir Ezzor.

The loss of Deir Ezzor province could be a serious setback for ISIL, as it holds oil reserves and is a key conduit for the jihadists to receive weapons and fighters from neighboring Iraq.

More than 1,700 people have been killed in the clashes between opposition militants and ISIL that began in early January, according to the Observatory.