Italy's navy on Thursday said it had rescued some 1,400 migrants from six boats intercepted crossing the Mediterranean over the past 24 hours, as smugglers take advantage of calm summer seas.

The rescues came as Libya's navy said it had retrieved the bodies of three would-be migrants and rescued almost 100 others after their boat sank off its coast.

The navy said 764 migrants were rescued from three boats overnight -- then 472 on two other boats intercepted on Thursday and around 200 more were on a sixth boat.

"The tally will be around 1,400 or 1,500 but we are still counting the latest ones," a navy official said.

The rescues were part of Rome's massive ongoing search and rescue mission, "Mare Nostrum" (Our Sea), after two shipwrecks in October in which over 400 migrants drowned.

Italy estimates around 100,000 migrants will have landed on its shores by the end of the year -- around the same number that arrived in 2011 in the wake of turmoil triggered by the Arab Spring revolutions in North Africa.

The navy said dozens of women and children were among the latest arrivals and released videos of the migrants wrapped in thermal blankets being transferred onto warships where they were checked by medical staff and images of a baby being carried to safety.

Many of the migrants come from Eritrea, currently under investigation by the UN Human Rights Council for alleged abuses including extrajudicial executions, torture and forced military conscription that can last decades.

The migrants rescued by the navy are usually taken to temporary centres in Sicily -- all already full. Many try to avoid registering asylum requests in Italy and make their way to other parts of Europe.