At least 30 people have been found dead in a fishing boat packed with hundreds of would-be migrants, according to the Italian navy.
The victims all apparently suffocated.
Rescuers found the bodies after boarding the vessel between Sicily and North Africa to attend to several people said to be in distress; among them two pregnant women.
Earlier this month, at least 39 people drowned off Libya after an overloaded, inflatable boat capsized while trying to cross to the Italian island of Lampedusa.
Authorities say more than 60,000 migrants have already landed in southern Italy this year, and that the record of 63,000 set in 2011 is likely to be broken.