DAMASCUS, Feb. 13 (Xinhua) -- At least 60 civilians have been killed and tens of others wounded over the past six days by Turkish shelling on the Syrian city of al-Bab, as part of the operation against the Islamic State (IS) group, which is in control of that key city in northern Syria, a monitor group reported on Monday.

As many as 13 children were among those killed in the Turkish shelling on al-Bab in the northern countryside of the northern province of Aleppo, near the Turkish borders, said the Syrian Observatory for Human Rights.

The UK-based monitor said intense battles are still raging between the Turkish forces and allied Syrian rebels on one side with the IS militants in the city, as the Turkish forces have captured areas in the western part of the city.

The Observatory said the IS is still in control over the major areas in al-Bab despite the fact that the Turkish forces and allied rebels have reached the outskirts of the city three months ago.

While the Turkish forces were on an offensive on IS from the northern, western and eastern parts 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.

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.