The situation is "desperate" at Syria's Bab al-Salameh border crossing where thousands of fleeing civilians are seeking to enter Turkey, medical charity Medecins sans Frontieres (MSF, Doctors without Borders) said on Monday.
"From what MSF can see the situation in A'zaz district is desperate, with ongoing fighting and tens of thousands of people displaced," said Muskilda Zancada, the charity's head of mission in Syria.
Zancada said that three hospitals MSF supports in the area had been bombed in recent days, but they were too close to current frontlines to allow the extent of the damage to be assessed.
An offensive by Syrian government forces backed by intense Russian airstrikes has cut off the A'zaz area from Aleppo city and other rebel territory and triggered an exodus to the border.
Turkey said on Sunday that it does not yet see a need to open its border to the refugees.
MSF said it was also concerned about "an impending food, water and fuel crisis in the coming weeks" in rebel-held eastern Aleppo city, as supply lines have been "nearly cut" to the area.
Meanwhile, Syrian state media and a monitoring group said government troops were pushing further north towards Tel Rifaat, south of A'zaz.
"The Syrian government forces and their allies are 5 kilometres away from Tel Rifaat, which is 20 kilometres from the Turkish border," Rami Abdel Rahman, head of the Britain-based Syrain Observatory for Human Rights, told dpa.
Abdel Rahman said capturing Tel Rifaat would be a further victory for the regime of President Bashar al-Assad, which is seeking to cut rebel supply lines from Turkey.