More than 300 people were believed to have been drowned. They were migrating to Europe seeking better life.
According to the International Organisation for Migration spokesman Jean-Philippe Chauzy strong winds could have caused the vessels to capsize.
Those who could swim were rescued, but authorities pulled 21 bodies from the waters. According to the group's figures, some 33,000 people crossed from North Africa to the Italian island of Lampedusa alone in 2008. Many of the boats are not seaworthy and deadly accidents are frequent.
One of the boats had been carrying 365 people although it was only supposed to hold 75, Libyan officials said. It was one of four migrant vessels that had sailed from Libya between Saturday, Mar, 28 and Sunday, Mar 29 apparently for Italy.