The UN has called for urgent aid access to Syria's Aleppo as regime forces and opposition fighters prepare to battle for control of the city, AFP reported Tuesday (August 9th).

Hundreds of thousands of civilians remain inside the city, where medical and food stocks "are running dangerously low", the UN's top humanitarian official in Syria, Yacoub El Hillo, and regional co-ordinator Kevin Kennedy said in a statement late Monday.

They appealed for a full-fledged ceasefire or weekly 48-hour "humanitarian pauses" to reach those in need.

UNICEF said children and families in Aleppo were facing "a catastrophic situation", with up to two million people without running water for four days after fighting damaged electricity networks needed to pump supplies.

"These cuts are coming amid a heatwave, putting children at a grave risk of waterborne diseases," Hanaa Singer, UNICEF's representative in Syria, said in a statement.

"Getting clean water running again cannot wait for the fighting to stop. Children's lives are in serious danger," Singer said.

The UN says two million people in the city are at risk, including up to 275,000 in east Aleppo. Other estimates put the total number of civilians in the city at about 1.5 million, with 250,000 in the eastern districts.

Sporadic clashes hit the edges of the city on Tuesday, but there were no signs yet of either side launching a large-scale offensive.

The Syrian Observatory for Human Rights confirmed clashes were taking place in Ramussa and said air raids on an opposition-held district of Aleppo killed three civilians on Tuesday morning.