Demanding a summit on the issue, Mr Renzi said trafficking was "a plague in our continent" and bemoaned the lack of European solidarity.

The 20m (70ft) long boat was believed to be carrying up to 700 migrants, and only 28 survivors have been rescued, BBC reported.

EU foreign ministers are expected to address the issue at a meeting later.

Human smugglers are taking advantage of the political crisis in Libya to use it as a launching point for boats carrying migrants who are fleeing violence or economic hardship in Africa and the Middle East.

Up to 1,500 migrants are now feared to have drowned this year alone.

The UN High Commissioner for Refugees (UNHCR) said the latest sinking could amount to the largest loss of life during a migrant crossing to Europe.

Governments across Europe have expressed dismay at Sunday's huge loss of life. But while the EU talks, the Mediterranean is turning into a graveyard.

The crisis highlights a fundamental weakness in the EU. Managing the situation requires political will, co-ordination and money from all the bloc's 28 countries. Not easy to achieve.

Last year, a record 170,000 people made the perilous crossing to Italy. Thousands died on the journey.