The number of Syrians trying to cross into Turkey amid an upsurge of fighting in northern Syria has nearly doubled, a Turkish official says.

The governor of the Turkish border province of Kilis said 35,000 refugees had reached the border area - up from an estimated 20,000 on Friday.

Turkey says it is prepared to help the refugees but the frontier remains shut.

They are fleeing a Syrian government offensive on rebel-held positions near the northern city of Aleppo.

In the past few days, the Syrian army - backed by Russian air strikes - has made a series of gains around Syria's largest city.

TURKEY’s ‘OBLIGATION’

On Saturday, Kilis Governor Suleyman Tapsiz said Turkey was able to help refugees inside Syria.

"Our doors are not closed, but at the moment there is no need to host such people inside our borders," he said.

Turkey has been providing food, shelter and blankets to thousands of civilians who are stranded on the Syrian side of the border.

The Turks have so far refused to open the border crossing.

EU Enlargement Commissioner Johannes Hahn on Saturday urged Turkey to do so.

"The Geneva convention is still valid which states that you have to take in refugees," Hahn said, as EU foreign ministers discussed the crisis in Amsterdam.

The call was echoed by Dutch Foreign Minister Bert Koenders, whose country currently holds the EU presidency.

"I look at these images of people standing at the Turkish border and I just wanted to underline the message people who are in humanitarian need should be allowed in," he said.