The Libyan justice minister, Mustafa Mohamed Abud al Jeleil, has resigned over "the excessive use of violence against government protesters," Libya's privately-owned Quryna newspaper has reported.
The newspaper said on its internet site that it had spoken to the minister by telephone. There was no immediate official confirmation of the resignation.
Libyan protesters celebrated in the streets of Benghazi on Monday, claiming control of the country's second largest city after bloody fighting, and anti-government unrest spread to the capital, with clashes in Tripoli's main square for the first time. Muammar Qaddafi's son vowed that his father and security forces would fight "until the last bullet".
Even as Seif al Islam Qaddafi spoke on state TV on Sunday night, clashes were raging in and around Tripoli's central Green Square, lasting until dawn on Monday, witnesses said. They reported snipers opening fire on crowds trying to seize the square, and Qaddafi supporters speeding through in vehicles, shooting and running over protesters. Before dawn, protesters took over the offices of two of the multiple state-run satellite news channels, witnesses said.
During the day on Monday, a fire was raging at the People's Hall, the main hall for government gatherings where the country's equivalent of a parliament holds its sessions several times a year. The pro-government news web site Qureyna said flames were seen leaping from the building, and that the headquarters of the Olympics Committee was also on fire.
Protesters were calling for a new protest at sunset on Monday in Green Square, setting up the likelihood of new clashes. Already, armed members of pro-government organisations called "Revolutionary Committees" were circulating in the streets hunting for protesters in Tripoli's old city, said one protester, named Fathi.
The city was shut down on Monday, with schools, government offices and most shops closed except a few bakeries serving residents hunkered down in their houses, said a Tripoli lawyer, Rehab.
The protests and violence were the heaviest yet in the capital of two million people, a sign of how unrest was spreading after six days of demonstrations in eastern cities demanding the end of the elder Qaddafi's rule.
Colonel Qaddafi's regime has unleashed the bloodiest crackdown of any Arab country against the wave of protests sweeping the region, which toppled the leaders of Egypt and Tunisia. More than 200 have been killed in Libya, according to medical officials, human rights groups and exiled dissidents.
British prime minister David Cameron, visiting neighbouring Egypt, called the Libyan government's crackdown "appalling."
"We can see what is happening in Libya which is completely appalling and unacceptable as the regime is using the most vicious forms of repression against people who want to see that country - which is one of the most closed and one of the most autocratic - make progress. The response they have shown has been quite appalling," he told reporters in Cairo.
Seif al Islam Qaddafi warned of civil war in Libya if protests continue, a theme continued on Monday on Libyan state TV, where a pro-regime commentator spoke of chaos and "rivers of blood" turning Libya into "another Somalia" if security is not restored.
Fragmentation is a real danger in Libya, a country of deep tribal divisions and a historic rivalry between Tripoli and Benghazi. The Arab world's longest ruling leader in power for nearly 42 years, Muammar Qaddafi has held an unquestioned grip over the highly decentralized system of government he created, called the "Jamahiriya," or "rule by masses."
Libya's former ambassador to the Arab League in Cairo, Abdel-Moneim al Houni, who a day earlier resigned from his post to side with protesters, issued a statement demanding that Colonel Qaddafi "be put on trial along with his aides, security and military commanders over the mass killings in Libya."
"Qaddafi's regime is now in the trash of history because he betrayed his nation and his people," Mr al Houni said.
The spiraling turmoil in Libya, an Opec country that is a significant oil supplier to Europe, was raising international alarm. Oil prices jumped $1.67 to nearly $88 a barrel on Monda.
Two leading oil companies, Statoil and BP, said they were pulling some employees out of Libya or preparing to do so. Portugal sent plane to pick up its citizens and other EU nationals and Turkey sent two ferries to pick up construction workers stranded in the unrest-hit country. EU foreign ministers were discussing on Monday the possible evacuation of European citizens. Mobs attacked South Korean, Turkish and Serbian construction workers at various sites around the country, officials from each country said.
The internet has been largely shut down in Libya, residents can no longer make international calls from land lines and journalists cannot work freely, but eyewitness reports trickling out of the country suggested that protesters were fighting back more forcefully. Most witnesses and residents spoke on condition they be identified by first name only or not at all, out of fear of retaliation.
In Libya's second largest city, Benghazi, protesters were in control of the streets Monday and took over the main security headquarters, known as the Katiba, after bloody clashes Sunday that killed at least 60 people, according to a doctor at the main hospital.
Cars honked their horns in celebration and protesters in the streets chanted "Long live Libya". Protesters took down the Libyan flag from above Benghazi's main courthouse and raised the flag of the country's old monarchy, which was toppled in 1969 by the military coup that brought Muammar Qaddafi to power, according to witnesses and video footage posted on the Internet.
Benghazi's airport was closed, according to an airport official in Cairo. A Turkish Airlines flight trying to land in Benghazi to evacuate Turkish citizens on Monday was turned away, told by ground control to circle over the airport then to return to Istanbul.
There were fears of chaos as young men - including regime supporters - seized weapons from the Katiba and other captured security buildings. "The youths now have arms and that's worrying," said Iman, a doctor at the main hospital. "We are appealing to the wise men of every neighbourhood to rein in the youths."
Youth volunteers were directing traffic and guarding homes and public facilities, said Najla, a lawyer and university lecturer in Benghazi. She and other residents said police had disappeared from the streets.
Benghazi has seen a cycle of bloody clashes over the past week, as security forces kill protesters, followed by funerals that turn into new protests, sparking new bloody shootings. After funerals on Sunday, protesters fanned out, burning government buildings and police stations and besieging the Katiba.
Security forces battled back, at times using heavy-caliber machine guns and anti-aircraft guns, according to residents. One witness said she saw bodies torn apart and that makeshift clinics were set up in the streets to treat the wounded. Ahmed Hassan, a doctor at the main Al Jalaa hospital, said funerals were expected Monday for 20 of those killed the day before, but that families of 40 others were still trying to identify their loved ones because their bodies were too damaged.
In some cases, army units reportedly sided with protesters against security forces and pro-Qaddafi militias. Mohamed Abdul-Rahman, a 42-year-old Benghazi merchant, said he saw an army battalion chasing militiamen from a security compound.
After seizing the Katiba, protesters found the bodies of 13 uniformed security officers inside who had been handcuffed and shot in the head, then set on fire, said Hassan, the doctor. He said protesters believed the 13 had been executed by fellow security forces for refusing to attack protesters.
Protest leaders and army units that sided with them were working to keep order in the streets on Monday, directing traffic and guarding homes and official buildings, several residents said.
On Sunday night, Colonel Qaddafi's son Seif al Islam took to state TV, trying to take a tough line in a rambling and sometimes confused speech of nearly 40 minutes.
"We are not Tunisia and Egypt," he said. "Muammar Qaddafi, our leader, is leading the battle in Tripoli, and we are with him."
"The armed forces are with him. Tens of thousands are heading here to be with him. We will fight until the last man, the last woman, the last bullet," he said.
He warned the protesters that they risked igniting a civil war in which Libya's oil wealth "will be burned". He also promised "historic" reforms in Libya if protests stop.
Seif has often been put forward as the regime's face of reform. Several of the elder Qaddafi's sons have powerful positions in the regime and in past years have competed for influence. Seif's younger brother Mutassim is the national security adviser, with a strong role in the military and security forces, and another brother, Khamis, heads the army's 32nd Brigade, which according to US diplomats is the best trained and best equipped force in the military.
Even as Seif spoke, major clashes had broken out for the first time in Tripoli.
Sunday afternoon, protesters from various parts of the city began to stream toward central Green Square, chanting "God is great," said one 28-year-old man who was among the marchers.
In the square, they found groups of Qaddafi supporters, but the larger number of protesters appeared to be taking over the square and surrounding streets, he and two other witnesses said. That was when the backlash began, with snipers firing down from rooftops and militiamen attacking the crowds, shooting and chasing people down side streets. they said.
Qaddafi supporters in pickup trucks and cars raced through the square, shooting automatic weapons. "They were driving like mad men searching for someone to kill. It was total chaos, shooting and shouting," the 28-year-old said.
The witnesses reported seeing casualties, but the number could not be confirmed. One witness, named Fathi, said he saw at least two he believed were dead and many more wounded.
After midnight, protesters took over the main Tripoli offices of two state-run satellite stations, Al Jamahiriya-1 and Al Shebabiya, one witness said.