Amid tight security on the Turkish side, hundreds of refugees – mostly women and children carrying bags of belongings – crossed the border from the Turkish town of Akcakale to Tel Abyad.

Syrian Kurdish-led forces captured Tel Abyad from ISIS last week, driving the militants away from the frontier in an advance backed by U.S.-led air strikes.

Security sources told Reuters that the border gate was subsequently kept closed for four days for security reasons.

More than 23,000 refugees fleeing fighting in northern Syria entered Turkey earlier this month, according to Turkish authorities cited by the U.N. refugee agency.

Turkey last week accused Kurdish forces in northern Syria of driving out civilians in areas it occupies, voicing concern at the displacement of Arabs and Turkmen from the area around Tel Abyad.

The Kurdish YPG militia has denied the allegations and urged civilians to return to cities controlled by Syrian Kurds, guaranteeing their safety.

Syria’s civil war has turned more than 3 million people into refugees — almost a fifth of the pre-war population. Turkey shelters 1.8 million Syrian refugees, meaning it has overtaken Pakistan to become the world’s leading host of refugees.

There are also around 7.6 million internally displaced people in Syria, according to the latest U.N. figures.