Turkey does not yet plan to let tens of thousands of civilians fleeing a Syrian government offensive and Russian airstrikes cross into its territory, a government spokesman in the border province of Kilis told dpa on Sunday.
Aid supplies are, however, being let through the Bab al-Salameh border crossing, the Turkish official and the UN's humanitarian coordination office confirmed.
Some 35,000 civilians have arrived at Bab al-Salameh and the nearby Syrian town of A'zaz, according to the UN Office for the Coordination of Humanitarian Affairs.
Many are sleeping in the open in overnight temperatures reaching minus 4 degrees Celsius.
Syrian government forces backed by intense Russian airstrikes this week broke rebel defences north of Aleppo, cutting off the northern countryside from Aleppo city and the rebel stronghold of Idlib to the south-west.
The offensive led to the collapse of peace talks in Geneva, with UN Syria envoy Staffan de Mistura saying he was pausing the talks and planned to resume on February 25.
Recent weeks have seen rebels, pounded by Russian airstrikes in support of President Bashar al-Assad, lose ground on key frontlines around Aleppo and in north-western and southern Syria.