Up to 700 feared dead after migrant boat sinks off Libya

Italian Prime Minister Matteo Renzi, who returned to Rome from a political event he was attending in Mantua, spoke by telephone to French President Francois Hollande. He was expected to hold a meeting with ministers later on Sunday.

The German government's representative for migration, refugees and integration, Aydan Ozoguz, said that with more arrivals likely to arrive as the weather turned warmer, emergency rescue missions should be restored.

"It was an illusion to think that cutting off Mare Nostrum would prevent people from attempting this dangerous voyage across the Mediterranean," she said.

Aid groups have called for the opening of a "humanitarian corridor" to ensure the safety of the migrants but there were also calls for action to prevent the boats from leaving.

The leader of the anti-immigrant Northern League party, Matteo Salvini, who has made migration one of the centrepieces of his political agenda, called for an immediate naval blockade of the coast of Libya.

"We need to stop the business of the people smugglers. We need to set up reception centres in Tunisia, Morocco, Egypt, Libya and wherever else is possible," he said.

Libya's lawless state, following the toppling of former leader Muammar Gaddafi in 2011, has left criminal gangs of migrant smugglers free to send a stream of boats carrying desperate migrants from Africa and the Middle East.

Around 20,000 migrants have reached the Italian coast this year, the International Organisation for Migration (IOM) estimates. That is fewer than in the first four months of last year, but the number of deaths has risen almost nine-fold.

In 2013, the previous government initiated the search-and-rescue operation "Mare Nostrum" or "Our Sea" after hundreds drowned in an incident off the coast of Lampedusa. The operation was cancelled last year, because of the cost and because some politicians said it encouraged migrants to depart by raising their hopes of being rescued.

Mare Nostrum made way for the European Union's border control mission, Triton. However Triton, which has a much smaller budget and which only operates within 30 miles of the Italian coast, has been criticised by humanitarian groups and Italy as inadequate to tackle the scale of the problem.