The UN high commissioner for human rights, Navi Pillay, called today for an international investigation into Libya's attacks on anti-government protesters, saying they may amount to crimes against humanity.
The UN security council was to meet at the urging of Libyan diplomats who defected in protest at the brutal crackdown and the Arab League was also to discuss the uprising which rights groups say has killed up to 600 people.
In a statement, Ms Pillay called for human rights violations to stop immediately and denounced "the reported use of machine guns, snipers and military planes against demonstrators".
Ms Pillay, a former UN warcrimes judge, said: "Widespread and systematic attacks against the civilian population may amount to crimes against humanity."
In addition, Ms Pillay supports the UN human rights council holding an emergency session on the situation in Libya, as demanded by many human rights groups. However, the decision is up to its 47 member states, Frej Fenniche, chief of the Middle East and North Africa section, told a news briefing in Geneva.
The forces of the Libyan leader Muammar Qaddafi have cracked down on demonstrators, with fighting spreading to the capital, Tripoli, after erupting in Libya's oil-producing east last week. The UN secretary general, Ban Ki-moon, has said Libya fired on civilians from warplanes and helicopters. He spoke personally with Mr Qaddafi, by telephone for 40 minutes on Monday and "forcefully urged him to stop the violence against demonstrators," a UN spokesman said.
Ms Pillay said: "The callousness with which Libyan authorities and their hired guns are reportedly shooting live rounds of ammunition at peaceful protestors is unconscionable. I am extremely worried that lives are being lost even as I speak."
Her office has no presence in Libya but stands ready to support investigations and promote civil, political and economic rights in the North African country.
The Libyan people are "tired of corruption", unemployment and of having their rights ignored, Ms Pillay said.
Through contacts with rights groups, Ms Pillay's office has drawn up a list of victims indicating around 250 people have been killed and hundreds injured during a week's violence.
However, Mr Fenniche said, "it seems that based on the situation on the ground and what we heard from many sources, that the number is higher than that.
"Many human rights defenders and journalists have been arrested. We don't know if they are alive or not," he said.
The International Committee of the Red Cross called on Libyan authorities to respect human life and apply international standards in using force to try to restore law and order.
"Those arrested and detained must be treated in conformity with international law," the ICRC said in a statement.
Mr Qaddafi, known for his sense of drama, made a lightning appearance on state television late Monday to scotch "malicious rumours" he had abandoned the oil-rich North African nation he has ruled for more than four decades.
"Were it not for the rain, I would have addressed the young people at Green Square and spent the night with them to prove I am still in Tripoli," he said in what the television advertised as a live broadcast from outside his home.
"It's just to prove that I am in Tripoli and not in Venezuela and to deny television reports, those dogs," Mr Qaddafi said as he stood under a silver umbrella about to step into a car.
Rain lashed Tripoli on Monday evening.
Despite the 22-second appearance, his grip on Libya appeared increasingly shaky as loyalists quit and two fighter pilots defected with their Mirage F1s to Malta on Monday rather than follow alleged orders to bomb Benghazi.
But state media were mobilised to forcefully deny the reports of massacres and an imminent collapse of the regime.
Al Jamahiriya Two state television said on a red ticker: "They say there are massacres in several cities, towns and neighbourhoods of Libya. We must fight against these rumours and lies." wrote.
However, Mr Qaddafi has been hit by defections in his diplomatic corps and the air force after it was allegedly ordered to attack civilians, and foreigners thronged to flee the violence which has cost up to 400 lives.
About 10,000 Egyptians were massed at the border in eastern Libya to escape overland, a security source in Cairo said, as hundreds of foreigners, mostly from Tunisia but also Egypt, scrambled for flights out of Tripoli.
"The airport is bursting at the seams. People spent last night there ... It's a mess," said a Tunisian engineer contacted by telephone.
A day after the revolt sparked in eastern Libya spread to the capital, several districts of Tripoli were calm early on Tuesday, including Tajoura which had seen violent clashes, witnesses told AFP.
Libya's state telecoms, meanwhile, said disruptions had been caused by a surge on the network, as Internet connections widely used to spread news of the revolt returned to normal and mobile phones were accessible early on Tuesday.
British Prime Minister David Cameron, on visit to Kuwait, said "reform -- not repression" was the way to guarantee stability in the Arab world. "Using force cannot resolve grievances, only multiply them," he warned.
Souhayr Belhassen, head of the International Federation for Human Rights (IFHR), quoted witnesses as saying militias and security forces loyal to Kadhafi were "breaking down doors and pillaging" to quell the revolt.
"It is impossible to remove the corpses from the road, we are shot at from above," one witness was quoted as telling a Libyan rights group.
Witnesses in Tripoli on Monday reported massacres in certain neighbourhoods of the capital after Libyan television announced that security forces were assaulting "dens of terrorists."
But Kadhafi's son, Seif al-Islam, quoted on the television, denied reports the armed forces had bombarded the cities of Tripoli and Benghazi to the east, after Al-Jazeera television reported raids in the capital.
With foreign countries drawing up evacuation plans, a security source in Egypt said the military was beefing up its deployment on the Libyan border in the face of a feared heavy influx of refugees.
Gunfire rattled overnight in Tripoli, where protesters attacked police stations and the offices of the state broadcaster, and set government buildings ablaze, witnesses told satellite news channels and human rights groups.
Rights groups say the government's crackdown has killed between 200 and 400.
More than 1,000 Chinese construction workers in Libya were forced to flee after gun-wielding robbers stormed their compound, stealing computers and luggage, their employer and state media in Beijing said.
Libya diplomats from the United Nations to Australia either resigned in anger, including Tripoli's ambassador to India, Ali al-Essawi, a former trade minister, or openly protested.
Libya's justice minister, Mustapha Abdeljalil, had also reportedly resigned in protest at "the excessive use of force."
Benghazi, Libya's second city and an opposition stronghold in the east, has fallen to anti-regime demonstrators after military units deserted, the Paris-based IFHR reported.
It said protesters also controlled Sirte, Tobruk in the east, as well as Misrata, Khoms, Tarhounah, Zenten, Al-Zawiya and Zouara, closer to the capital.
