- Italian navy said 40 migrants dead, more than 300 rescued
- More than 2300 migrants have died in 2015 attempting to cross the Mediterranean Sea
Additional details about how the 40 died were not immediately available.
The navy said that it had transferred the survivors to the Norwegian supply ship Siem Pilot, which is patrolling the central Mediterranean as part of the ongoing European Union effort to assist seafaring migrants.
Last month the Siem Pilot ferried 785 migrants safely to port after the Italian coast guard rescued them from a wooden boat and a rubber dinghy off the Libyan coast.
Saturday's episode is the latest in a string of disasters in the Mediterranean in what has been a deadly year for migrants at sea.
The International Organization for Migration (IOMC) said more than 2,300 migrants have died making the journey from sub-Saharan Africa to Europe in 2015, already making it the deadliest on record.
Rescues off the Italian and Greek coasts meanwhile are occurring at a rate of more than 1,000 migrants per day, according to IOMC.
"These latest tragedies underscore the dangers faced by migrants in the Channel of Sicily, now the deadliest route for those fleeing violence, natural disasters and abject poverty," the migration agency said in a statement.
IOMC predicts the number migrants arriving on European shores will reach a quarter-million by the end of August, a number that would surpass the total number from 2014.