The United Nations says an immediate pause in fighting is needed to allow the water and electricity networks to be fixed.
Some two million people are without vital supplies, the UN says.
Fighting between government forces and rebels has intensified in recent weeks.
At least 250,000 people are believed to have been trapped in rebel-held areas of eastern Aleppo since a key route into the area was closed by government forces in early July.
On Sunday, rebels cut off the government's key access route into western Aleppo.
