Italian Prime Minister Matteo Renzi listens to a reporter's question during a joint news conference with his Maltese counterpart Joseph Muscat at Chigi Palace in Rome, April 20, 2015. [Photo/Agencies]

Libya chaos

If the toll is confirmed in Sunday's tragedy, as many as 1,800 migrants will have died so far trying to cross the Mediterranean since the start of this year. The IOM estimates around 21,000 have made the voyage successfully.

In comparison, by the end of April 2014, fewer than 100 had died out of an estimated 26,000 who crossed.

The number of migrants normally surges in the summer, meaning far greater numbers are likely to attempt the voyage in the coming months. In total last year, 174,000 made the journey successfully and around 3,200 died.

The IOM says hundreds of thousands of people could be planning to attempt the crossing from Libya, now in a lawless state with two competing governments at war with each other and both incapable of policing people-smuggling gangs.

Renzi said a military operation in Libya was not on the table, while Malta's Muscat said the United Nations should mandate a force to fight human traffickers in Libya.

Human rights group Amnesty International said Thursday's summit would be a litmus test of Europe's commitment to save lives in the Mediterranean, calling for a robust rescue mission.

Bernard Ryan, professor of migration law at Leicester University, told Reuters: "It's a myth to think there's some other solution".

Last week around 400 migrants were reported to have died attempting to reach Italy from Libya when their boat capsized.

Northern EU countries have so far largely left rescue operations to southern states, such as Italy. According to the IOM, Italian coast guard, navy and commercial ships had rescued 10,000 migrants in the Mediterranean in the past few days.