A Reuters photographer at the scene said many of them were women and children and they had entered Turkey through a make-shift border crossing between official gates. Turkish gendarmerie officers oversaw the transfer, he said.

Islamic State is in control of the border town in Hasaka province. The hardline group last week launched a counter-offensive in the provincial capital, Hasaka city, that is divided into zones run separately by the government of President Bashar al-Assad and a Kurdish administration.

"There are 2,000 people today that are being processed," a Turkish official said, explaining that they undergo registration and health checks before being allowed to enter.

"They are escaping coalition bombardments as well as YPG advancement," he said, referring to the Kurdish militia and US-led coalition giving aerial support to Kurds.

Local media had reported a buildup of refugees waiting to cross in recent days.

The Turkish official said since last week 6,837 people were admitted in the area, and 686 of them were Iraqi nationals.

The northeastern corner of Syria is important because it links areas controlled by Islamic State in Syria and Iraq.

Syrian Kurds have also sought to expand their territorial control over a region stretching from Kobani to Qamishli they see as part of a future Kurdish state.