Fighting between interim government forces and those loyal to Muammar Gaddafi on Monday halted a Red Cross convoy’s passage into the Libyan city of Sirte.
The vehicles were forced to turn back from the deposed Libyan leader’s birthplace amid gun battles between the two sides.
The International Committee of the Red Cross said the humanitarian situation there is deteriorating because food, water, fuel and medical supplies are running out.
Earlier on Monday the former rebels launched a new offensive on Sirte after a three-week siege.
Resistance from Gaddafi loyalists has so far frustrated their efforts to take the town.
The former Libyan leader’s whereabouts remain unknown.