Colonel Muammar Gaddafi has denied reports he has fled Libya, after fresh anti-government protests took place and cracks formed within the ruling elite and army.
The leader of 41 years gave a brief statement, saying: "I am in Tripoli and not in Venezuela. Don't believe those dogs."
British Foreign Secretary William Hague said earlier there was evidence to suggest that Col Gaddafi may be fleeing to the south American country.
A senior source in President Hugo Chavez's government had denied the claims and they were also dismissed by Libyan deputy foreign minister Khalid Kayem.
It comes after unconfirmed reports of military aircraft firing at crowds in the capital Tripoli and mercenaries shooting at protesters.
Justice minister Mustapha Abdel Jalil has become the latest senior official to resign and other figures close to the ruling elite have condemned the bloodshed.
Libya's UN ambassadors are calling for Col Gaddafi to step down, further undermining his 41-year rule.
Meanwhile, two Libyan air force jets have arrived in Malta, where military officials say their pilots have asked for political asylum.
In the capital Tripoli, anti-government protesters reportedly ransacked the state television headquarters and set the central government building and a police station on fire.
Witnesses said protesters moved into the capital's Green Square last night, and were then attacked by security forces and militia in clashes that lasted until dawn.
Foreign journalists are banned from Libya, making it difficult to confirm reports coming out of the country.
Violent clashes have also been seen in Benghazi, the country's second largest city, and several other towns.
Medical officials, human rights groups and exiled dissidents say hundreds of people have been killed since the unrest began about a week ago.
A doctor working in Benghazi's general hospital, Dr Ahmed, told Sky News the fatalities there were now near 300.
According to reports on state TV, several people have been killed by security forces in what it described as a sweep against "terrorists".
Earlier, Col Gaddafi's son insisted his father was still in charge.
In an unscripted and seemingly threatening address on state television, Saif Gaddafi said his father would fight "until the last man, the last woman, the last bullet".
Cracks within Col Gaddafi's regime are beginning to emerge.
Mohamed Bayou, who was chief government spokesman until a month ago, said the leadership was wrong to use violence against its opponents and called on Saif Gaddafi to start talks with the opposition.
"I hope that he will... change his speech to acknowledge the existence of an internal popular opposition, to enter into dialogue with them regarding thorough changes in the Libyan system," he said.
The Warfalah Tribe, one of the country's largest, has backed the protesters.
In a statement from tribal elders, the group denounced "the hideous crimes of Gaddafi and his regime".
"(We) call upon all our brave sons and daughters, throughout Libya, to fully rebel against this enemy of God and his regime who murdered their own people in cold blood," the statement said.
A group of Libyan Muslim leaders also added their voices to the discontent, urging all Muslims to rebel against the leadership.
Security forces are now said to be operating a "shoot to kill" policy, using high velocity live ammunition on unarmed protesters.
Anti-government protester Khaleel Suwelhi, in Tripoli, said the capital was the main battleground.
"Most cities have been overwhelmed by protesters," he said.
"All the security forces have surrendered or joined the protesters, the only city left is Tripoli and there were many clashes there yesterday night."
An activist with the Libyan Youth Movement, who only wanted to be known as Ahmed, told Sky News protesters were willing to either "die or win".
He and Libyan exile Zeyad Matter alleged African mercenaries had been drafted in by Col Gadaffi to defend his regime because sections of the military had defected.
Ahmed said: "I have spoken to some of my relatives in the country and they are saying that those African mercenaries are going into the hospitals and killing those who are there."