At least 40 migrants died at sea and more than 320 others were rescued Saturday by the Italian navy from an overcrowded smugglers' boat in the Mediterranean Sea north of Libya, authorities said.
The navy said because the rescue was still ongoing it couldn't give exact numbers of dead.
"They are still counting the victims," Interior Minister Angelino Alfano told reporters after giving the figure of 320 rescued.
RaiNews24 TV, reporting from the navy rescue coordination center in Rome, said the dead migrants were found in the hold of an overcrowded smugglers' boat.
Some 2,100 migrants have died at sea this year trying to make the crossing from the shores of Libya, where human traffickers are based, to Italy. They are fleeing war, persecution and poverty in the Middle East, Africa and Asia.
The number of migrants trying to reach Europe by sea is on track to hit a record this year, according to the Geneva-based International Organisation for Migration.
Greece has reported 134,988 arrivals from Turkey this year, the group said, while Italy has rescued 93,540 newcomers through July.
Along with migrants landing in Spain and Malta, 237,000 people have made the crossing so far this year, the agency says — compared to 219,000 for all of 2014.