Kurdish officials and an activist group say Syrian Kurdish fighters are just outside of a key Islamic State-held town on the Turkish border.

The advance on Tal Abyad could allow Kurds to cut off a vital route that the extremists use to bring in new foreign fighters. US-led airstrikes have aided their push.

Kurdish official Idriss Naasan said Sunday that Islamic State fighters have fled from Suluk, a few kilometres southwest of Tal Abyad, and that Kurds now hold the town.

The Britain-based Syrian Observatory for Human Rights also said Islamic State fighters had withdrawn. The Observatory said the Kurds are about 5 kilometres from Tal Abyad.

Hundreds in Tal Abyad stood close to the barbed wire marking the Turkish border yesterday, trying to cross to safety.