Colonel Muammar Gaddafi has issued a defiant message, calling on supporters to "fight and kill" the rebels who now control large parts of Libyan capital Tripoli.
The comments came as opposition forces stepped up their search for the dictator and Foreign Secretary William Hague said the despot's rule was "finished".
But Mr Hague acknowledged that the battle for control of Libya was "not over yet" as pockets of Gaddafi loyalists continued to offer resistance.
In an audio message broadcast on Al-Arabiya television, Gaddafi said: "Don't leave Tripoli for the rats. Fight them, fight them, and kill them."
Nato has provided reconnaissance and intelligence assistance to the National Transitional Council (NTC) to help the manhunt for the dictator and Mr Hague said the alliance would continue to protect civilians as fighting continued.
As opposition forces scoured Tripoli in search of Gaddafi, regime spokesman Moussa Ibrahim insisted Gaddafi was "leading the battle for our freedom".
Mr Hague, speaking after chairing a meeting of the Government's National Security Council, said: "There is no way back for the Gaddafi regime and clearly many of its key members are on the run.
"But there remain forces active loyal to the Gaddafi regime, concentrated particularly in the south of Tripoli and around the city of Sirte.
"As long as that remains the case and they remain a threat to the civilian population, the Nato operations will continue.
"So this is not over yet. The regime is finished - but fighting, as everyone can see from their television screens, is not over yet."
Defence Secretary Liam Fox confirmed that Nato was providing "intelligence and reconnaissance assets" to the NTC but refused to comment on a report that elite British SAS soldiers were leading the hunt for the dictator and his sons.
Amid scenes of heavy fighting, opposition fighters surrounded an apartment complex in Tripoli, claiming that Gaddafi or some of his sons were inside.
With Libya largely under the control of opposition forces, attention has turned to the country's future.
Mr Hague said "enormous progress" had been made in recent days and that the priority now was to give the NTC diplomatic support to build a "free, democratic and inclusive future for Libya".
A conference in Paris to be led by Prime Minister David Cameron and French President Nicolas Sarkozy will provide an opportunity for the NTC to set out its plans for the future.
Mr Hague said the UK was also "highly active" in efforts to unfreeze 1.5 billion US dollars of Libyan assets following the Gaddafi regime's collapse. Mr Cameron has spoken to South African president Jacob Zuma, who has concerns about the move.
Mr Hague said: "We welcome their agreement that five hundred million dollars can be released for immediate humanitarian purposes. We would now like to see a further billion dollars released."
Officials in Scotland were trying to contact Libyan rebel leaders as part of efforts to track down the Lockerbie bomber Abdelbaset al-Megrahi.
As part of the terms of his release on compassionate grounds Megrahi is supposed to check in with officials at East Renfrewshire Council, but he has not been reached since fighting broke out in Tripoli.
Scottish Justice Secretary Kenny MacAskill said attempts were being made to reach the NTC.