DAMASCUS - Turkish forces and allied Syrian rebels entered the city of al-Bab on Saturday, the last stronghold of the Islamic State (IS) group in northern Syria near the Turkish borders, a monitor group reported.

The Turkish forces and the rebels it's backing under the umbrella of the Euphrates Shield succeeded to storm al-Bab after weeks of battles aiming to strip the IS of its largest remaining stronghold near the Turkish borders in the countryside of the northern province of Aleppo, according to the Syrian Observatory for Human Rights.

The UK-based watchdog group said the Turkish forces and allied militants were clashing with the IS in the northern and western part of the city, as the Syrian army is closing in on the city from its southern rim.

While the Turkish forces were on an offensive on IS from the northern, western and eastern part of the city, 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, or the northern city of al-Raqqa, the de facto capital of the terror-designated group.

A military source said on Saturday that the Syrian army is a few kilometers away from al-Bab, adding that IS militants have executed 40 civilians in the city over the past 24 hours, for unclear reasons.

Observers said the attacks on al-Bab were coordinated between the Russians and the Turks, until recently when the Syrian army clashed with the Euphrates Shield rebels near al-Bab, during which the Russian artillery "accidentally" fired and killed three Turkish soldiers and wounded 11 others.

The situation was later contained and the battles were refocused on IS again in al-Bab, which is important for both the Syrian army and the Turkish forces.

For the Syrian army, securing the southern rim of al-Bab means securing the vicinity of the northern city of Aleppo from the attacks of IS.

As for the Turks, capturing the northern part of the city cut the way in the face of the growing Kurdish influence in northern Syria, a red line drawn by Turkey.

Speaking of the Kurds, the complexity of the situation in northern Syria which reflects the conflict in the international interests have apparently delayed the Kurdish growing control, but pushed them to hasten to attack al-Raqqa, the self-declared capital of IS, as by such a move they can make up for the areas Turkey has taken in the north before the Turkey-backed rebels reach al-Raqqa.

The Observatory said Saturday that the Kurdish fighters of the Syrian Democratic Forces are closing in on the outskirts of al-Raqqa city amid battles with the IS.