The 40-year rule of Col Muammar Gaddafi is under threat amid spiralling unrest throughout Libya.
Several senior officials - including the justice minister - have reportedly resigned after security forces fired on protesters in Tripoli overnight.
Witnesses say renewed protests have hit two suburbs of the capital.
In an earlier TV address, Col Gaddafi's son Saif al-Islam conceded that the eastern cities of al-Bayda and Benghazi were under opposition control.
But he warned of civil war and vowed that the regime would "fight to the last bullet".
The BBC's Jon Leyne, in neighbouring Egypt, says Col Gaddafi has now lost the support of almost every section of society.
Reliable sources say Col Gaddafi has now left the capital, our correspondent adds.
'Hatred of Libya' After clashes in the capital overnight were suppressed by security forces, state TV reported a renewed operation had begun against opposition elements there.
"Security forces have started to storm into the dens of terror and sabotage, spurred by the hatred of Libya," the Libyan TV channel reported.
An eyewitness in Tripoli told the BBC that the suburbs of Fashloom and Zawiyat al-Dahmani had been cordoned off by security forces.
Protesters were out on the streets and flames and smoke could be seen rising from the area, the witness said.
Amid the turmoil on the streets, senior officials have also begun to desert the regime.
Justice Minister Mustapha Abdul Jalil quit the government because of the "excessive use of violence", the privately owned Quryna newspaper reported.
In New York, Libya's deputy ambassador to the UN denounced the Gaddafi government, accusing it of carrying out genocide against the people.
Libya's envoy to the Arab League, Abdel Moneim al-Honi, announced he was "joining the revolution", and its ambassador to India, Ali al-Essawi, told the BBC he was also resigning.
In another blow to Col Gaddafi's rule, two tribes - including Libya's largest tribe, the Warfla - have backed the protesters.
Meanwhile, two helicopters and two fighter jets from Libya landed in Malta.
The helicopter was said to be carrying French oil workers.
The fighter pilots, both colonels, took off from a base near Tripoli after they had been ordered to bomb protesters, Maltese officials quoted by Reuters news agency said.
The agency said one of them had asked for asylum.