The NATO military alliance will stand by Turkey if it proves necessary to protect the country from attacks by the group calling itself Islamic State (ISIL), NATO Secetary General Jens Stoltenberg said on Monday.

This comes as ISIL militants raised their flag on a building on the outskirts of the Syrian border town of Kobani, just one kilometre away from Turkish territory.

“Turkey should know that NATO will be there if there is any spillover, any attacks on Turkey as a consequence of the violence we see in Syria,” said Stoltenberg.

Kobani’s Kurdish defenders said ISIL fighters had not reached the city centre.

A black ISIL flag was visible from across the Turkish border, close to some of the most intense clashes in recent days.

“ISIL have only planted a flag on one building on the eastern side of town,” said Ismail Eskin, a journalist in the town. “That is not inside the city, it’s on the eastern side. They are not inside the city. Intense clashes are continuing.”

Fighting has been raging between Kurdish and ISIL fighters who have battled to control the predominantly Kurdish town for almost three weeks.

Turkey meanwhile has beefed up its military presence along the volatile frontier with Syria.

Ankara had so far taken a back seat in the battle against ISIL but it has vowed to protect its own borders.

Over a dozen Turkish tanks appeared to take up defensive positions on a hill in the Turkish town of Mursitpinar, just across the border from Kobani.