Ships manned by humanitarian organisations, the Italian navy and the coast guard have helped rescue about 4500 boat migrants as calm seas returned to the Mediterranean, prompting a surge in departures from North Africa.
Rescue operations are continuing after a woman's corpse was taken from a large rubber boat and other migrants were collected from about 40 different vessels, an Italian coastguard spokesman said on Thursday.
The Topaz Responder, a ship run by the Malta-based humanitarian group Migrant Offshore Aid Station (MOAS), earlier said about 24 migrant boats had been spotted in waters about 20 nautical miles from the Libyan port city of Sabratha.
Libya's navy intercepted about 1000 migrants on board eight rubber boats off Sabratha on Thursday morning, spokesman Ayoub Qassem said. He said the migrants were from Arab and sub-Saharan African countries.
"The mass movement is probably the result of week-long, unfavourable weather conditions" that have come to an end, MOAS said on Twitter.
The Topaz Responder picked up 382 sub-Saharan African migrants from three different large rubber boats. The Bourbon Argos, a ship run by humanitarian group Doctors without Borders, rescued 1139 migrants from 10 boats and two other humanitarian vessels picked up 156 more.
The Italian navy said it rescued 515 people from two dinghies, German humanitarian group Sea-Watch said it had 100 onboard, and the Italian coast guard, which coordinates rescue operations, has deployed several boats.
An agreement between Turkey and the EU to stop migrant departures for the Greek islands has reduced boat arrivals by 98 per cent during the first five months of the year from the same period of 2015, the International Organization for Migration (IOM) said.
But arrivals in Italy continue at about the same rate as last year, and the deadly central Mediterranean route has already claimed 2438 lives, IOM said.