At least 60 people were killed in a car bombing in a Syrian village on Friday, a British war monitor said on Friday.
The suicide bombing that rocked the town of Susian, in said to be targeting Turkey-backed rebels,
The Syrian Observatory for Human Rights said most of the causalities were rebels.
The IS group announced its withdrawal from al-Bab, came after 100 days of battles against the Turkish forces and allied Syrian rebels fighting in an operation called the Euphrates Shield.
The Syrian army succeeded recently to besiege al-Bab from its southern edge, a move to prevent IS fighters to withdraw toward other stronghold in the eastern province of Deir al-Zour, the de facto capital of IS.