He said violations of human rights had been carried out by Muammar Gaddafi's regime, and more than 1,000 had died.

Mr Ban said 22,000 people had fled Libya via Tunisia, and a further 15,000 via Egypt.

"Much larger numbers are trapped and unable to leave," he added. "There are widespread reports of refugees being harassed and threatened with guns and knives."

He said it was important for neighbouring countries, including those in Europe, to keep their borders open to those fleeing the violence.

Mr Ban also said that there was a food crisis inside Libya that the UN World Food Programme (WFP) expected to worsen. The WFP says Libya's food supply chain is at risk of collapse because imports have not been getting into the country and food distribution is hampered by violence.

Diplomats at the UN Security Council say Britain and France have drawn up a draft resolution with a package of measures aimed at isolating Libya's political and military leaders. As well as targeted sanctions, this could include an arms embargo, and a proposed referral of the situation in Libya to the International Criminal Court.