Libya's navy says some 100 migrants are believed missing at sea and that at least 279 others have been rescued off the Libyan coast.
Wednesday's statement says the migrants, mostly Africans, had embarked on the perilous trip across the Mediterranean in several vessels. Those missing were all from one single rubber boat that got ruptured while at sea.
The navy says the survivors, who were found on Tuesday, were taken a naval base in the capital, Tripoli.
On Sunday, the Libyan navy said it rescued 272 migrants.
Libya descended into chaos following the 2011 uprising that toppled and killed longtime dictator Moammar Gadhafi. It has since become a frequently used route to Europe for those fleeing poverty and conflict.
Libya has increased efforts to stem the flow of migrants.