Over 4,200 migrants, who were sailing across the Mediterranean sea, were rescued and 17 corpses were found on several of the rickety boats by the Italian coastguard.
Distress calls were made from 22 different boats, many off Libya but also off the southern Italian coast.
The total number of people rescued in 24 hours is one of the highest in recent years but the coastguard could not confirm if it was a record. So far, the busiest days this year have been the rescue of 3,791 migrants on April 12 and 3,690 on May 2.
The 17 bodies were found on three inflatable dinghies, from which more than 300 other migrants were rescued alive, the Italian navy said on Twitter on Friday.
The navy's press office was not immediately able to say how the migrants died.
But the Italian authorities have in the past spoken of the harsh conditions faced by the migrants at sea, where they have to endure extreme weather changes and are at risk of hunger, thirst and violence on board the often crammed and flimsy vessels.
Friday's rescue operations were led by the Italian coastguard and included the help of Italian, German and Irish naval ships working under the EU's Frontex border agency.
A similar international maritime rescue mission on Thursday saw more than 700 migrants helped to safety off the coast of Sicily after they had set sail from Libya in six boats.
Overall, more than 40,400 boat migrants, many of them fleeing conflict and poverty in countries such as Syria and Eritrea, have arrived in Italy since the start of the year, similar to the same period last year.
So far this year, some 1,770 migrants have perished on the hazardous journey to Europe, according to a latest International Organization for Migration (IOM) report which does not include Friday's rescue.
The huge spike in the number of people trying to cross the Mediterranean Sea in recent weeks has been attributed to the worsening security situation in Libya, as well as milder weather.
After a string of deadly shipwrecks that sparked global alarm, EU ministers this month approved plans for a military operation to fight people smugglers in the Mediterranean, although proposals to destroy traffickers' boats in Libyan waters still need UN approval.
The European Commission also unveiled plans to make the rest of the 28-nation EU share the burden of frontline states such as Italy, Greece and Malta when it comes to taking in migrants, although some countries such as Britain opposed.
This year's massive numbers are level with last year when authorities registered 41,243 arrivals between January and May 31. A difference is however being felt in Greece which has registered 37,000 arrivals since the beginning of the year, already 3,000 more than in the whole of 2014, said Di Giacomo, spokesperson for IOM.