Ten migrants who attempted to cross the Mediterranean and reach Europe were found dead on Sunday, as the Libyan coastguard intercepted five boats carrying 500 people and ordered them to return.
The latest deaths came the day after nearly 5,800 migrants were rescued at sea, according to the Italian coastguard. The number rescued on Saturday was one of the highest recorded in a single day, raising fears that the tide of desperate people trying to reach Europe from Africa and the Middle East has not been slowed by recent disasters.
"Around 10 people were found dead," the Italian coastguard said, while several rescue teams worked in the waters off war-torn Libya, where most of the rickety, overcrowded boats set sail from.
Rescuers said most of the latest fatalities were on board distressed migrant boats which were intercepted. It was unclear how they had died. Another three men drowned after they jumped into the sea, as they rushed to reach a coastguard vessel.
The Italian navy said its patrol ship Bettica picked up more than 400 migrants from two vessels on Sunday, among them some 60 women and around 15 children.
Meanwhile the Libyan coastguard intercepted five boats with some 500 people on board, some eight nautical miles off the coast, and ordered them to head back for the city of Misrata east of the capital Tripoli.
Colonel Reda Issa told AFP that most of the migrants were Africans.
He did not say what would happen to those intercepted, but Libya has a detention centre for migrants in Misrata.
People smugglers have taken advantage of the chaos gripping Libya since the 2011 uprising toppled dictator Moamer Kadhafi.
On April 19, some 750 migrants were killed when their trawler sank between Libya and southern Italy, sparking global outrage and demands for action.
Four days later EU leaders tripled the bloc's budget for patrols off Libya. EU leaders are now seeking UN Security Council approval for military action against smugglers in chaos-ridden Libya. But rights groups have blasted the Europe for focusing on patrols rather than humanitarian efforts.