TRIPOLI (Reuters) - Libya's unrest spread to the capital Tripoli on Sunday after scores of protesters were killed in the second city Benghazi, which appeared to have slipped out of control of forces loyal to strongman Muammar Gaddafi.
Gaddafi has attempted to put down protests with a violent crackdown, triggering some of the worst bloodshed in the two months since unrest began sweeping across the Arab world.
In the first sign of serious unrest in the capital, thousands of protesters clashed with supporters of Gadaffi in Tripoli. Gunfire could be heard and police using tear gas to disperse the demonstrators.
In Benghazi, centre of Libya's unrest, tens of thousands of people took to the streets and appeared to be in control of the city before security forces opened fire and killed scores.
Benghazi residents said soldiers from a unit had joined their protest and defeated a force Gaddafi's elite guards. Bodies were brought to a hospital riddled with bullets and wounds from rocket-propelled grenades.
A witness in Tripoli said police in the capital were using tear gas against protesters, some of whom were throwing stones at billboards of Gaddafi.
A resident of the capital told Reuters by telephone he could hear gunshots in the streets. "We're inside the house and the lights are out. There are gunshots in the street," he said. "That's what I hear, gunshots and people. I can't go outside."
An expatriate worker said protesters were being dispersed by police and he could see burning cars in the capital.
The spread of unrest to Tripoli is a major development as protests so far, the biggest of Gaddafi's rule, were mostly confined to the east of the country where his grip is weaker.
One of Gaddafi's sons, Saif al-Islam Gaddafi, appeared on television delivering a rambling address in which he repeatedly said Libya was "not Egypt or Tunisia," neighbouring countries whose strongmen were swept from power in recent weeks.
Wagging a finger at the camera, he blamed Libyan exiles for fomenting the violence, promised dialogue on the Libyan constitution and warned of bloodshed if the situation slipped further out of control.
In Benghazi, Habib al-Obaidi, head of the intensive care unit at the main Al-Jalae hospital, said the bodies of 50 people, mostly killed by gunshots, were brought there on Sunday afternoon. The deaths came after scores were killed on Saturday.
Two hundred wounded people had arrived, 100 of them in serious condition, he said.
"The problem is not the number of those killed but how they were killed. One of the victims was obliterated after being hit by an RPG to the abdomen," he said.
Members of an army unit known as the "Thunderbolt" squad had come to the hospital carrying wounded comrades, he said. The soldiers said they had defected to the cause of the protesters and had fought and defeated Gaddafi's elite guards.
"They are now saying that they have overpowered the Praetorian Guard and that they have joined the people's revolt," another man at the hospital who heard the soldiers, lawyer Mohamed al-Mana, told Reuters by telephone.
Human Rights Watch said the death toll had reached 233 killed in five days of violence.
In a rare sign of dissent, Libya's representative to the Arab League quit in protest over "oppression against protesters," Al Jazeera television reported.
The leader of the Al-Zuwayya tribe in eastern Libya, Shaikh Faraj al Zuway, threatened to cut oil exports to Western countries within 24 hours unless authorities stopped what he called the "oppression of protesters."
Akram Al-Warfalli, a leading figure in the Al Warfalla tribe, one of Libya's biggest, told Al Jazeera: "We tell the brother (Gaddafi), well he's no longer a brother, we tell him to leave the country."
Libya is a major energy producer with significant investment from Britain's BP Plc, Exxon of the United States and Italy's ENI among others.
Communications are tightly controlled and Benghazi is not accessible to international journalists, but the picture that has emerged is of a city slipping from the grasp of security forces in the biggest challenge to Gaddafi's rule since the "brotherly leader" seized power in a 1969 military coup.
Sunday's violence took place after residents took to the streets in their thousands to bury scores of dead killed in the previous 24 hours. The United States said it was "gravely concerned" by what it called credible reports hundreds of people had been injured or killed.
A leading tribal figure in the city who requested anonymity said security forces had been venturing out of their barracks and shooting protesters in the street. Clashes were taking place on a road leading to a cemetery where thousands had gone to bury the dead. Buildings were on fire, he said.
One witness said thousands of people had performed prayers in front of 60 bodies laid out in Benghazi in the morning. Women and children were among hundreds of thousands that came out onto the Mediterranean seafront and the area surrounding the port.
(Additional reporting by Hamid Ould Ahmed in Algiers, Suleiman al-Khalidi in Amman, Tom Heneghan in Paris; Writing by Christian Lowe and Marie-Louise Gumuchian; Editing by Diana Abdallah and Jon Boyle)