The U.N.'s emergency relief coordinator says his organization and humanitarian partners are working to provide food, water and medical aid as a Syrian government offensive in Aleppo sends tens of thousands fleeing toward the border with Turkey.

Stephen O'Brien said Monday he is gravely concerned by reports that over 30,000 civilians, mostly women and children, have been forced from Aleppo and other areas of northern Syria following heavy clashes and aerial bombardment by the Syrian government and its allies.

He says reports indicate that civilians have been killed in the fighting and at least two hospitals have been hit.

Meanwhile, O'Brien says camps for displaced people near the Turkish border are full and running beyond the U.N. and aid groups' response capacity.