A surge in fighting in Syria's Aleppo province has displaced about 50,000 people, the International Committee of the Red Cross (ICRC) has warned.
The humanitarian situation is deteriorating rapidly, the ICRC added, with water supplies to Aleppo city cut.
The Syrian government is attempting to recapture rebel-held parts of the major city backed by Russian air power.
Turkey is under pressure to allow in 30,000 Syrian refugees stranded on its border.
In a statement, the ICRC said supply routes for aid had been cut, putting civilians under "enormous pressure".
"The temperatures are extremely low and, without an adequate supply of food, water and shelter, displaced people are trying to survive in very precarious conditions," said the head of the ICRC in Syria, Marianne Gasser.