Thousands of refugees have gathered at the UNHCR tent camp in Ras Jdir, Tunisia, at the border with Lybia [EPA]
The United Nations are sending a humanitarian assessment team to Tripoli, a request that was agreed to by Musa Kusa, the Libyan foreign minister.
In a telephone conversation, Ban Ki-moon, the UN secretary general, urged Kusa to "consider the best interests of the Libyan people, and listen to the united voice of the international community".
He also called on the authorities in Tripoli to uphold their responsibility to protect the country's citizens and to heed the Libyan people's legitimate aspirations to live in dignity and peace.
Ban has appointed Abdelilah Al-Khatib, the former foreign minister of Jordan, as his special envoy to Libya to undertake consultations with the Libyan government on the humanitarian situation of the crisis.
Al-Khatib will travel to New York in the next few days before taking up his responsibilities in the region.
The secretary-general has expressed deep concern about the fighting in Libya, "which is claiming large numbers of lives and threatens even more carnage in the days ahead," according to a statement from his office.
He noted that civilians are bearing the brunt of the violence, and called for "an immediate halt to the government's disproportionate use of force and indiscriminate attacks on civilian targets".
He also stressed that those who violate international humanitarian law or commit grave crimes must be held accountable.
Muammar Gaddafi, the Libyan leader who has lost control of swathes of the country to opposition forces, said the African Union was also sending a fact-finding committee that would show that reports about problems were a lie.
Gaddafi said he was in regular contact with African states, adding: "I said to them that there is nothing that calls for the situation to be exaggerated, as if there were a problem. Everything is normal."
"They are always in touch and in fact the African Union will send a committee to investigate the facts to confirm to the world that what is published about Libya outside is a lie, 100 per cent," he said.
Vaclav Havel, the Czech ex-president and communist-era dissident, said on Monday that military action on Libya by Western countries would be necessary if the armed conflict lasts.
"Especially if it drags on and if Gaddafi keeps boarding himself up and committing further crimes, some action will be necessary," Havel told the business daily Hospodarske noviny in an interview.
"It may take different shapes: aid to local rebels, an air space blockade or a targeted attack on places where Gaddafi is hiding," Havel said.
US defence planners are said to be preparing a range of land, sea and air military options in Libya in case Washington and its allies decide to intervene, The New York Times reported late Sunday.
Citing unnamed administration officials, the newspaper said just simple use of signal-jamming aircraft in international airspace could muddle Libyan government communications with military units.
Administration officials said preparations for such an operation were under way, the report said.