Libyan rebel forces are trying to push towards Col Gaddafi's hometown of Sirte, having taken most of Tripoli.
But they have faced fierce resistance from Gaddafi loyalists on the approach to the city, which is still under loyalist control.
There are reports of fresh fighting in Tripoli, which had mostly been quiet overnight.
The rebel government leader Mahmoud Jibril has appealed for urgent aid to avert a humanitarian crisis.
Basic supplies and power are running low - the National Transitional Council (NTC) has said it urgently needs $5bn (£3bn) to prevent further destabilisation.
The UN is expected to vote this week on a resolution to release some $1.5bn (£1bn) of assets that were frozen under sanctions.
Some $500m has been released, but South Africa has stalled Washington's attempts to release more, saying it wants to wait for guidance from the African Union, which has not recognised the rebel leadership.
The rebel fighters advancing towards Sirte were 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," rebel commander Fawzi Bukatif was quoted as saying by AFP news agency.
"We thought they would surrender with the fall of Tripoli."
Col Gaddafi's sprawling Bab al-Aziziya compound was overrun on Tuesday. Firefights continued on Tuesday but by Wednesday, correspondents said there was only some sporadic incoming fire.
The rebel fighters have been breaking into the complex tunnel system underneath the compound, searching for Col Gaddafi and his fighters. The bodies of several Gaddafi fighters have been found inside.
Fighting erupted in the capital again on Thursday afternoon. There were reports of fighting in the Abu Salim district and near the Corinthia Hotel about 1.5km (a mile) from Martyrs Square (formerly Green Square), where most foreign journalists are based.
In other developments:
- Four Italian journalists who were abducted by suspected Gaddafi loyalists on Wednesday have been freed
- The Arab League has said it gives its full backing to the NTC as the legitimate representative of the Libyan people
- UK Defence Minister Liam Fox has confirmed that Nato is providing intelligence and reconnaissance assistance to rebels hunting Col Gaddafi
- A ship that can carry 300 people is due to leave Tripoli's port to evacuate some of the foreign nationals waiting to leave
- The International Monetary Fund says it will recognise the NTC as Libya's leaders when there is "a clear, broad-based, international recognition"
The head of the NTC cabinet, Mr Jibril, has travelled to Italy to seek foreign help in accessing Libya's frozen funds. He said they needed "urgent help".
"Our priorities cannot be carried out by the government without having the necessary money immediately," Mr Jibril said after talks in Rome with Italian Prime Minister Silvio Berlusconi.
"Our people did not receive their salaries for months so we are telling our friends that the biggest de-stabilising element would be the failure of the NTC not to deliver the necessary services and pay the salaries of the people which were not paid now for almost four months."
Mr Berlusconi has promised to release more than 350m euros of Libyan assets frozen in Italian banks.
The NTC's 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.
Medical charity Medecins Sans Frontieres says there is also an urgent need for basic medical supplies - including anaesthetic and antibiotics - and for trained medical staff.
'Dead or alive'
Col Gaddafi's whereabouts are unknown, though rebels have said they think he is still in or around Tripoli.
A spokesman for Col Gaddafi, Moussa Ibrahim, has said he is safe and "leading the battle for our freedom and independence every day".
The rebels have announced an amnesty for anyone within his "inner circle" who captures or kills him.
The head of the NTC, Mustafa Abdul Jalil also said the NTC supported an offer by a group of businessmen to pay $1.7m for Col Gaddafi, "dead or alive".
Col Gaddafi 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.
In the last audio message believed to be from him, the fugitive leader vowed to fight until victory or martyrdom.