Colonel Muammar Gaddafi has issued a defiant message, calling on supporters to "fight and kill" the rebels who now control large parts of the 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".
However 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.
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. The regime is finished - but fighting, as everyone can see from their television screens, is not over yet."
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 and Mr Hague said the priority now was to give the NTC diplomatic support to build a "free, democratic and inclusive future for Libya".
Meanwhile, 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.