UNITED NATIONS — Three quarters of a million people have fled Libya since Moamer Kadhafi's forces launched an offensive against anti-government demonstrators, the UN humanitarian chief said Monday.

"The conflict, the breakdown of state infrastructure and shortages of cash and fuel are causing serious problems to the population of Libya," Valerie Amos, UN chief humanitarian coordinator, told the UN Security Council.

The United Nations could not give an accurate figure for the number of casualties since the conflict erupted in mid-February.

But more than 746,000 people have fled the country, about 5,000 are stranded at border points in Egypt, Tunisia and Niger and some 58,000 are displaced in eastern Libya, Amos said.

"Widespread shortages are paralyzing the country in ways which will impact gravely on the general population in the months ahead, particularly for the poorest and the most vulnerable," Amos told ambassadors from the 15-nation council.

UN humanitarian workers were pulled out of Tripoli after the UN compound was ransacked on May 1, just after a coalition air raid which killed one of Kadhafi's sons.

"The government has apologized for the incident and offered full compensation for the damage caused," Amos said, adding that new security guarantees had been given by the government.

"It is our intention to return as soon as possible to Tripoli and open land access to Misrata, the western mountains and other affected areas."

Rebel-held Misrata has been under attack by Kadhafi forces for more than two months and hundreds are said to have been killed there.

"Some people are running short of food, water and other basics. Medical facilities need supplies and trained personnel," Amos said.

More than 13,000 people have been evacuated from the western city, which normally has a population of about 300,000, but Amos said up to 300 third country nationals are still stranded there.

The UN has appealed for about 300 million dollars for its Libyan humanitarian operation and so far received about 144 million dollars, Amos said.