Syrian Kurdish fighters announced on Monday that they have seize control of the Islamic State-held city of Tal Abyad, cutting off a major supply route to Raqqa, the jihadist group's de facto capital.

"The whole city is under our control and there is no more fighting," Huseyin Kocher, a Kurdish commander in Tal Abyad told the BBC. "Our people should know that we are going to clean all the remnants of ISIS in northern Syria."

The fighting has resulted in thousands of civilians fleeing to nearby Turkey.

The Kurdish forces are being supported by Syrian rebel groups and airstrikes from the US-led coalition forces.

The capture of Tal Abyad allows the Kurdish forces to connect the other areas they control along the Turkish border, from Iraq in the east to Kobane in the west.

Tal Abyad is only around 50 miles away from Raqqa, the ISIS' stronghold. With the city now in Kurdish hands, the ISIS lost a direct route to bring in fresh supplies or foreign fighters, whom the jihadists has depended on more and more to carry out suicide bombings that have pushed out Iraqi forces.

The US has found a reliable partner in the Syrian Kurdish force, also known as the People's Protection Units or YPG, who have taken more than 200 Kurdish and Christian towns in northeastern Syria, as well as strategic mountains claimed by Islamic militants.

Kurdish official Idriss Naasan said on Sunday that ISIS fighters have fled from Suluk, a few miles southwest of Tal Abyad, and that the town is now held by the Kurds.

The soldiers at the Turkish border, meanwhile, keep the extremists at bay from the north.

There is still a lot to do, however. Rami Abdurrahman, chief of the Observatory, clarified that ISIS still has in its hands the road linking the Turkish border with Raqqa.

Kurdish YPG units advancing from the east and west began their assault on Tal Abyad on Sunday, after days of fierce skirmishes where they were able to capture a number of villages.

The Kurdish attack and US-led airstrikes forced more than 16,000 Syrian civilians to flee their homes and cross the border with Turkey.

However, the refugees briefly found themselves stranded at the border fence over the weekend after Turkey closed the crossing, with Turkish authorities saying they would only allow the refugees to enter in the event of a humanitarian tragedy.

Nevertheless, dozens of the refugees managed to cross the border by cutting holes in the fence. They were immediately rounded up on the Turkish side of the border by Turkish troops.

Turkish authorities later opened the gate and allowed the rest of the refugees to pass. Up to 3,000 refugees arrived at the crossing on Monday, according to Turkish news sources.