The UN Refugee agency (UNHCR) said Friday that up to 1,200 people fleeing Libya may have died in the Mediterranean Sea since the conflict in the North African country began, dpa reported.
"There are about 12,000 people who have arrived in Italy or Malta and we believe that as many as 1,200 people are dead or have gone missing," said Melissa Fleming, a spokeswoman for the Geneva-based UNHCR.
The agency also cited an account by a migrant who said that unidentified military vessels off the Libyan coast failed to pick up a boat carrying 72 people, most of whom subsequently died of exhaustion, thirst or starvation in late March or early April.
Earlier this week the French military rejected allegations that its Charles de Gaulle aircraft carrier left migrants to die in the Mediterranean Sea in March.
The denial followed a report by the London-based Guardian newspaper that a boat carrying 72 migrants had drifted in open waters for 16 days after running out of fuel 18 hours after setting off from Tripoli, on March 25.
All but 11 of the migrants, who were trying to get to the Italian island of Lampedusa, had died of hunger and thirst, the Guardian said, adding the warship was "likely to have been the French ship Charles de Gaulle."
It was not immediately clear if the account provided by the migrant to the UNCHR and the report by the Guardian referred to the same vessel.
Meanwhile on Friday six vessels carrying a total of around 1,250 mostly sub-Saharan African migrants from Libya arrived at Lampedusa and, as in recent weeks and months, put a strain on reception facilities on the small Italian island.
Italian coast guard officials said that another vessel carrying more than 100 migrants was spotted some 40 nautical miles from the island which lies on a tract of the Mediterranean between Sicily and North Africa.
Another smaller boat carrying around a dozen migrants was intercepted by a coast guard patrol in the same area, officials said.
Friday's arrivals are the latest in an exodus of migrants towards Lampedusa that began in January with thousands of Tunisians fleeing from the uprising in their country that led to the overthrow of former president Zine El Abidine Ben Ali.
Since March, when the current revolt against Libyan leader Moamer Gaddafi began, most of the migrants trying to reach Lampedusa have come from Libya.
Earlier this week, United Nations aid agencies appealed to the European Union and NATO to increase their efforts to rescue refugees crossing the Mediterranean Sea from Libya in unsafe boats.
The appeal came after reports that a boat with 600 people aboard sank off the coast of Libya last week. Dozens of people were feared to have drowned in the incident.