A fishing boat carrying immigrants trying to reach Europe - sailing from Libya - capsized and sank Wednesday off the coast of Greece, authorities said, leaving at least 79 dead and many more missing, The Associated Press (AP) said, adding that the coast guard, navy and merchant vessels and aircraft fanned out for a vast search-and-rescue operation set to continue overnight. 

It was unclear how many passengers were missing, but some initial reports suggested hundreds of people may have been aboard when the boat went down dozens of miles from shore, AP reported. 

Greek authorities said 104 people were rescued after the boat sank in international waters some 75 kilometers (45 miles) southwest of Greece’s southern Peloponnese peninsula. 

"The spot is close to the deepest area of the Mediterranean Sea, and the depth could hamper any effort to locate a sunken vessel." AP said.