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.
In other developments:
- About 120 fighters on both sides were killed around the town of Ratyan, north of Aleppo, on Friday, the UK-based Syrian Observatory for Human Rights said.
- Syrian FM Walid al-Moualem warned the country will resist any intervention and the aggressors would be sent home "in coffins", in what is seen as a reference to Saudi Arabia's statement that it may join such an operation.
- Nato accuses Russia of "undermining" Syrian peace efforts - including the suspended talks in Geneva - through its strikes, a claim denied by Moscow
- Russia and Turkey trade accusations of preparing an invasion in Syria
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.
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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," Mr 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.
Since Syria's war erupted almost five years ago, Turkey has had an "open-door policy" for refugees, now hosting more than 2.5 million.
But on Saturday it was announced that the border will not open for the latest exodus from Aleppo.
It is a sign of the nightmare unfolding in Syria's largest city, where opposition-held areas are being pounded by Russian strikes and attacks by the Assad regime.
If it is surrounded, more than 300,000 people inside could be trapped and the opposition could be dealt a fatal blow.
Half of Syria's pre-war population have fled their homes. Turkey has long been the gatekeeper to sanctuary.
And as the fight for Aleppo intensifies, many more will try to come, posing Turkey the dilemma: does it give safe passage or does it decide a limit has been reached?
In November, the EU clinched a deal with Turkey, offering it £2.3 billion to care for Syrian refugees on Turkish soil.
On Thursday, 60 donor countries meeting in London pledged billions of dollars to ease the plight of Syrian refugees.
About 4.6 million people have fled Syria during the civil war that began in 2011. Another 13.5 million are said to be in need of humanitarian assistance inside the country.
Turkey hosts the largest number of refugees - 2.5 million.
The Syrian war and Aleppo
- March 2011: Anti-government protests erupt across Syria, but Aleppo is initially untouched as a result of a state crackdown.
- July 2012: The battle for Aleppo begins. Rebels make swift advances, but are unable to consolidate their gains and the city becomes divided.
- 2013: The government begins bombarding rebel districts with barrel bombs, causing thousands of casualties.
- February 2016: The government captures towns north of Aleppo, threatening to encircle the city.