Egypt has boosted its military near the border and set up field hospitals, as thousands of its nationals return.
Several countries are evacuating their citizens and oil companies are relocating expat staff.
Correspondents in Tripoli say the capital is calm but there is a sense of intimidation after a night of fighting.
Overnight Libyan leader Col Muammar Gaddafi dismissed reports that he had fled amid the unrest sweeping the country, calling foreign news channels "dogs".
Speaking to state TV from outside a ruined building, he said: "I am in Tripoli and not in Venezuela," after rumours that he had flown to Caracas.
Meanwhile, UN human rights chief Navi Pillay said attacks on civilians could amount to crimes against humanity.Continue reading the main story A correspondent BBC News, Tripoli
Colonel Gaddafi's short, bizarre appearance was described as disgraceful here. People were angry that he didn't address the situation in the country. No mention of the fear that he'd spread among people, and no mention of the orders he'd given to bomb Tripoli and Benghazi.
But they are also happy to know he is still in town so he can be tried inside Tripoli. "We want him to stay here and pay for what he's done," said a Tripoli resident.
Tripoli seems to be quiet after a frightening night. People are intimidated and staying at home. Shops are closed. There are few cars on the roads. There are long queues for petrol and longer ones for bread.
A couple of streets that we drove past have evidence of burning and riots. There is a very heavy army presence in and around sensitive areas, especially where there is a diplomatic presence. Evening is the time to watch out.
Yet people seem to be determined to continue. Looking at what people achieved in Benghazi, they are encouraged. There are no police, no army and no officials there. The army is still in control of the suburbs of the city and the airport.In a statement, Ms Pillay condemned the "callousness with which Libyan authorities and their hired guns are reportedly shooting live rounds of ammunition at peaceful protesters".
The UN Security Council is to meet in closed session to discuss Libya later in the day.
The Arab League will also hold an emergency session.Airport 'destroyed'
Egypt's ruling military council said it had sent reinforcements to the main border crossing, the Salum passage, following a withdrawal by Libyan border guards.
Around 10,000 Egyptian nationals based in their western neighbour are fleeing the violence. Thousands have already returned from Libya since the protests began almost a week ago.
The Egyptian army has set up two field hospitals on the border to deal with the sick and injured.
Egypt says it will send at least four aircraft to evacuate its citizens.
But Foreign Minister Ahmed Aboul Gheit said the airport at Benghazi had been destroyed and there were problems getting flight permits."We know there are about one million to 1.5 million Egyptians in Libya, therefore we recommend to our citizens that you stay in your homes, stay off the streets, secure yourselves with water and food," he said.
Meanwhile unconfirmed media reports said at least 300 foreign construction workers employed by a South Korean company, about 100 of them from Bangladesh, were being held against their will, possibly by protesters, in the eastern port of Darnah.
There are about 50,000 Bangladeshis currently working in Libya.
In other developments;China has urged Libya to ensure the safety of its citizens after reports that hundreds of Chinese construction workers in Ajdabiya were forced to flee an armed attackThree Turkish ships have been sent to Benghazi to evacuate about 3,000 nationals. A thousand have already been airlifted to safetyItaly is to send three C-130 air force planes to evacuate its citizens. The former colonial power has about 1,500 nationals resident in LibyaThe US has ordered all non-emergency personnel to leave LibyaThe UK foreign office is advising Britons to leave if they can, although most of the 3,500 resident in Libya are thought to have already left. The remainder have been advised to take commercial flights, but airlines British Airways and BMI have cancelled all flights on TuesdayOil company Royal Dutch Shell says all its expatriate staff have been "temporarily relocated". Italy's Eni and France's Total are also evacuating staffMultiple fronts
A BBC correspondent in Tripoli says that while there is a heavy police presence in the capital, the second city, Benghazi, is in opposition control and there is no sign of security forces.
"People have organised themselves to get order back to the city. They have formed committees to run the city," said eyewitness Ahmad Bin Tahir.
Reports that military aircraft had fired on protesters in Tripoli on Monday have been backed up by Libyan diplomats who have turned against the leadership.
But Col Gaddafi's son Saif al-Islam said the aircraft had been used only to bomb army bases which had defected to the opposition.Libya's most senior diplomat in the US, Ali Aujali, has criticised Col Gaddafi's regime in a BBC interview
The BBC's Jon Leyne, in western Egypt, says the regime now seems to be fighting on multiple fronts, trying to put down the protests and fighting a bitter battle against a growing number of army units that have risen up against the Libyan leader.
Libya's diplomats at the United Nations in New York called for international intervention to stop the government's violent action against street demonstrations in their homeland.
Deputy Permanent Representative Ibrahim Dabbashi said Libyans had to be protected from "genocide", and urged the UN to impose a no-fly zone.
Ali Aujali, Libya's most senior diplomat in the US, also criticised the country's leader. He told the BBC he was "not supporting the government killing its people".
Meanwhile Libyan state TV denied there had been any massacres, dismissing the reports as "baseless lies" by foreign media.Continue reading the main story Col Muammar Gaddafi has led since 1969Population 6.5m; land area 1.77m sq km, much of it desertPopulation with median age of 24.2, and a literacy rate of 88%Gross national income per head: $12,020 (World Bank 2009)Opposition control Our correspondent says Col Gaddafi has now lost the support of almost every section of Libyan society.
Foreign journalists work under tight restriction in Libya, and much of the information coming from the country is impossible to verify.
But the authorities have accepted that eastern cities such as al-Bayda and Benghazi - traditional pockets of resistance to the government - are now under the control of the opposition.
The unrest did not touch Tripoli until Sunday, when hundreds of protesters flooded the streets, only to be suppressed by security forces. Witnesses say more than 50 people have been killed.
Before the unrest spread there, Human Rights Watch estimated that 233 people had been killed. Other groups said the figure was much higher.
The violence has helped to push up oil prices to their highest levels since the global financial crisis of 2008.
This post was made using the Auto Blogging Software from WebMagnates.org This line will not appear when posts are made after activating the software to full version.