Aid agencies operating in the Mediterranean Sea say they are looking for safe ports in Malta and Italy for nearly 500 migrants rescued during the last 72 hours after sailing from Libya.
The agencies, Médecins Sans Frontières (MSF) and SOS Méditerranée, said some of those rescued were suffering from hypothermia and dehydration.
Others had been exposed to fuel, which can develop into burns.
A spokesman for MSF said that despite the bad winter weather, boats were continuing to leave Libya.
The migrants have spoken of the deteriorating security situation in the country.
An internationally brokered truce between the un-recognised government of national accord in Tripoli and the rival military commander, Khalifa Haftar, has broken down.