Five people died in a migrant shipwreck off the coast of Libya and 562 survived it, the Italian Navy said Wednesday on Twitter, revising down a previous death toll of seven.
A migrant boat in distress was spotted by a patrol unit just before it overturned because of "the high number of people on board," Italy's Marina Militare said in a separate statement.
Its patrol vessel rushed to the scene with lifeboats and life jackets. Further rescue units, including a helicopter, were immediately deployed to support rescue attempts.
The Mediterranean is the world's most dangerous sea migration route: 1,357 people have drowned or gone missing in it since the start of the year, the International Organization for Migration (IOM) reported last week.
In another Wednesday operation, the Italian navy intercepted a second distressed boat and picked up 108 people, bringing to 670 the day's tally of rescued migrants.
Migrant crossings to Italy have surged this week: late on Tuesday, the Italian Coast Guard said 5,600 people had been picked up from the sea since Monday, in 38 separate interventions.
Interior Minister Angelino Alfano said Italy was committed to saving all found in danger off its coast.
"We rescue migrants first, then we ask if they are refugees [to be given asylum] or irregulars [to be repatriated]," the minister said in Rome.
Speaking before the latest rescues, IOM Rome spokesman Flavio Di Giacomo told dpa that there had been 39,600 migrant landings in Italy since the start of 2016, broadly stable from the same period of 2015.