At least 45 migrants died and dozens more were missing after their boats capsized in the Mediterranean Sea on May 27, the Italian coastguard said.
Around 14,000 people were taken off often flimsy vessels over the whole week, the United Nations and the coastguard said, and hundreds more may have drowned, although there were no official estimates of total casualties.
The Italian Navy ship Vega rescued about 135 people off a "half-submerged" large rubber boat in one of 17 operations coordinated by the coastguard on May 27.
The Vega recovered 45 bodies and is still searching for the missing, the navy said, marking the third straight day of reports of migrant deaths at sea.
The coastguard said warmer weather and calmer seas have led to a surge in people trying to cross from Libya, where people-smugglers operate freely.
The migrants, many of whom do not know how to swim and do not have life jackets, paid hundreds or thousands of dollars to make the crossing.