The BBC's Jim Muir: "There are thousands upon thousands of people waiting desperately to cross that border"
The situation on Libya's border with Tunisia has reached crisis point, as tens of thousands of foreigners flee unrest in the country, the UN says.
Aid staff are battling to cope with an exodus that has seen some 140,000 people crossing into Tunisia and Egypt.
The UN has suspended Libya from its Human Rights Council and has called for a mass humanitarian evacuation.
Libyan leader Col Muammar Gaddafi has played down protests and is trying to regain control of areas in the west.
He is facing a massive challenge to his 41-year rule, with protesters in control of towns in eastern Libya.
Witnesses said pro-Gaddafi forces tried to retake the western cities of Zawiya, Misrata and Nalut on Monday but were repulsed by rebels helped by defecting army units.
There are fears in Zawiya that the city may be attacked from the air, but the rebels remained defiant.
"We're not here for power, authority or money," they said in a message aimed at Col Gaddafi.
"We are here for the cause of freedom and the price we are willing to pay is with our own blood. It's victory or death."
Protesters holding Nalut and the town of Zintan, 145km (70 miles) south-west of Tripoli, both reported the approach of Gaddafi forces and said they feared fresh attacks.
In voting to suspend Libya from the UN Human Rights Council, the resolution - passed by consensus by the UN membership - accused Libya of committing gross and systematic violations of human rights.
General Secretary Ban Ki-moon said: "These UN actions send a strong and important message - a message of great consequence within the region and beyond - that there is no impunity, that those who commit crimes against humanity will be punished, that fundamental principles of justice and accountability shall prevail."
The BBC's Barbara Plett at the UN says this resolution seals Col Gaddafi's isolation as it is the body that represents all member states - the one where Libya might have expected to have some support and it has none.
The UN says the situation on the Tunisian-Libyan border has reached "crisis point"
The UN High Commissioner for Refugees said an estimated 40,000 people, mostly Egyptians, were still waiting at the border trying to cross from Libya into Tunisia.
It said it was urgently appealing, along with the International Organisation for Migration, for governments to engage in "a massive humanitarian evacuation of tens of thousands of Egyptians and other third country nationals".
World Food Programme executive director Josette Sheeran told the BBC food was being brought in by road and air, and bought locally, but supplies were under "deep stress".
"This will be a very pressured situation for some time - that's why we have launched an emergency appeal for funds to back up the system here," she said.
Tented transit camps are being set up hurriedly on the Tunisian side, while frantic efforts are being made to charter aircraft and ships to repatriate the stranded.
In other developments:
The European Union is calling an extraordinary summit for 11 March to discuss the situation in Libya and unrest in other parts of North Africa and the Middle East
US Secretary of State Hillary Clinton, in testimony to the US House of Representatives Foreign Affairs Committee, urged lawmakers not to cut funds on dealing with overseas crises. She said Libya "could become a peaceful democracy or it could face protracted civil war"
The Red Cross is requesting access to western Libya, amid unconfirmed reports of attacks on doctors and summary killings of patients
Col Gaddafi gave an interview in the capital Tripoli for BBC Middle East editor Jeremy Bowen, US TV network ABC and the UK's Sunday Times newspaper.
Col Gaddafi accused Western countries of abandoning Libya and said that they had no morals and wanted to colonise the country.
When asked whether he would resign, he said he could not step down as he did not have an official position - and insisted that the power in the country was with the people.
Col Gaddafi challenged those, including UK Prime Minister David Cameron, who have accused him of having money abroad, to produce evidence. He said he would "put two fingers in their eye".
Col Gaddafi said true Libyans had not demonstrated but those who had come on to the streets were under the influence of drugs supplied by Osama Bin Laden's al-Qaeda network.
But in response to the interview, the US ambassador to the UN Susan Rice said the fact he was laughing at questions while "slaughtering his own people" showed that he was disconnected from reality.
Col Gaddafi's son, Saif al-Islam Gaddafi, on Tuesday condemned Ms Rice's comments and added that Mr Cameron's handling of the situation was "like a joke".
Mr Cameron has frozen Gaddafi assets and called for the Libyan leader to go.
Saif Gaddafi told Sky News that the east had not fallen and he denied that the people there wanted his father out, saying it was just local difficulties.