At least 30 persons were killed in a suicide bombing in Syria's Susian town on Friday, a monitor group reported.

The bombing targeted Turkey-backed rebels who along with Turkish forces captured nearby Al Bab city a day earlier after dislodging the Islamic State (IS) militant group out of that key area near the Turkish border, media reported.

The Syrian Observatory for Human Rights said most of the casualties were rebels. Other activists placed the number of deaths at 50.

A day earlier, the IS announced its withdrawal from Al Bab, which has been taken by the Turkish forces and allied Syrian rebels on Thursday.

The withdrawal of the IS from Al Bab, its largest stronghold in northern Syria near the Turkish borders, came after 100 days of battles against the Turkish forces and allied Syrian rebels fighting in an operation called the Euphrates Shield.

The IS claimed it had killed 400 Turkish soldiers and rebel fighters.

For the Turks, capturing the northern part of the city will help reduce the growing Kurdish influence in northern Syria, a red line drawn by Turkey.

The Syrian Army has succeeded in besieging Al Bab from its southern edge, a move to prevent IS fighters from withdrawing toward other strongholds in the eastern province of Deir al-Zour, or the northern city of al-Raqqa, the de facto capital of the terror group.

Observers said the attacks on Al Bab were coordinated between the Russians and the Turks.