Libyan rebel forces are pushing east towards Col Gaddafi's hometown of Sirte, having taken most of Tripoli.
They have been exchanging heavy rocket fire with about 1,000 Gaddafi loyalists on the road to the city and are bringing up reinforcements.
Gaddafi forces are still firmly in control of the eastern city as well as Sabha in the desert to the south.
But with supplies and power running short, there are warnings of an impending humanitarian crisis in Libya.
Rebels advancing towards Sirte were also said to be blocked in the town of Bin Jawad as loyalists kept up stiff resistance.
"Gaddafi's forces are still fighting, we are surprised. We thought they would surrender with the fall of Tripoli," rebel commander Fawzi Bukatif is quoted as saying by the AFP news agency.
Meanwhile, the head of the rebels' National Transitional Council's (NTC) cabinet, Mahmoud Jibril, said the NTC was seeking $2.5bn (£1.5bn) in immediate aid.
Its immediate priority is to cover humanitarian costs and pay employees' salaries, though in the longer term, money will be needed to repair Libya's oil infrastructure, correspondents say.
The NTC also says it has started the process of moving its headquarters from Benghazi to Tripoli, but that with Gaddafi loyalists still fighting back, a full move has been postponed until next week at the earliest.
Col Gaddafi's whereabouts are unknown, though rebels have said they think he is still in or around Tripoli.
In other developments:
Four Italian newspaper journalists who were abducted by suspected Gaddafi loyalists on Wednesday have been freed, Italian media report.
Late on Wednesday, the US presented a draft resolution at a meeting of the UN Security Council asking it to release $1.5bn of assets for humanitarian needs. A vote is expected on Thursday or Friday.
South Africa has been stalling Washington's attempts over the resolution, saying it wants to wait for guidance from the African Union, which has not recognised the rebel leadership as Libya's legitimate authority.
The head of the National Transitional Council's (NTC) cabinet, Mahmoud Jibril, is due to hold talks with Italian Prime Minister Silvio Berlusconi in Milan on Thursday.
UK Defence Minister Liam Fox confirms Nato is providing intelligence and reconnaissance assistance to rebels hunting Colonel Gaddafi.
'Dead or alive'
The rebels entered the capital, Tripoli, four days ago, where most of the fighting seems to be over.
Col Gaddafi's sprawling Bab al-Aziziya compound was overrun on Tuesday, though there were firefights within the complex on Wednesday.
Rebel commanders said hot spots remained, with snipers and rocket explosions still dangerous.
The rebels have announced an amnesty for anyone within Col Gaddafi's "inner circle" who captures or kills him, and a $1.7m (£1m) reward.
The head of the NTC, Mustafa Abdul Jalil, announced the amnesty offer from the eastern city of Benghazi, adding the NTC supported an offer by a group of businessmen to pay $1.7m for Col Gaddafi, "dead or alive".
Col Gaddafi also faces an arrest warrant issued by the International Criminal Court on charges of crimes against humanity.
The rebel leadership have also offered Col Gaddafi safe passage out of the country, if he renounces his leadership.
The fugitive leader has vowed in an audio message to fight until victory or martyrdom.
