The Libyan regime has been accused of deliberately pushing African migrants to board unsafe refugee boats bound for Europe.
"The authorities (in Libya) are not discouraging, at all, in fact there may be signs that they are encouraging these boat journeys," a spokeswoman for the UN High Commissioner for Refugees said.
Already 14,000 people, mostly from sub-Saharan Africa, have used Libya as a springboard to reach Europe, and thousands more are poised to make the treacherous sea journey in the coming weeks as weather in the Mediterranean improves.
Some who fled to Tunisia and Egypt when fighting broke out are now crossing back into Libya because it is easier to get onto smugglers' boats there. Others are arriving from elsewhere in Africa.
"Even though you have to cross through a conflict zone to reach these boats there might even be people attracted to taking this chance from Africa," said the spokeswoman.
The flow of migrants from Libya to Italy almost stopped after the two countries signed an agreement in 2008 for Tripoli to automatically take people back. That deal broke down when Rome joined Nato's effort to police the UN-mandated no-fly zone over Libya.
The UN refugee agency has asked countries to consider permanently taking in up to 6,000 migrants. So far it has received offers of 900 places from 11 countries.