Italian officials say a boat carrying immigrants sank off the coast of Italy, killing at least 78 people.
Antonio Candela, the government's health commissioner for Palermo, is quoted by LaPresse news agency as saying 159 people have been rescued, but that the boat is believed to have been carrying some 500 people, meaning around 250 are still unaccounted-for.
Reuters reported the vessel sank off the Sicilian island of Lampedusa.
Passengers reportedly threw themselves into the sea as the vessel got into trouble and Italian officials were quoted as saying that dozens of people were still in the water.
Earlier this week, 13 migrants drowned while trying to reach Sicily.
There are reports that a fire broke out on board, before the boat sank. The mayor of Lampedusa, Giusi Nicolini, described the scene as a "continuous horror".
At this time of year, when the Mediterranean tends to be calmer, vessels carrying migrants from Africa and the Middle East land on Italy's southern shores almost every day, reports the BBC's Alan Johnston, but often the vessels are overcrowded and are not seaworthy. Over the years, many have died when their boats have sunk.
The UN said almost 500 people were reported dead or missing at sea during 2012 in attempts to reach Europe.
NBC News and the BBC contributed to this report. Check back for further updates.