At least 80 migrants are feared dead after a boat capsized off the coast of Tunisia. Four people were rescued from the inflatable vessel - which sank in waters near the town of Zarzis - but one died later in hospital, reports said.The three Malians who were rescued said that they had set out from Zuwara in Libya. The country is a main departure point for migrants hoping to reach Europe.Libya has been torn by violence and division since long-time ruler Muammar Gaddafi was deposed and killed in 2011.Thousands of migrants, many from sub-Saharan Africa, are being held in detention camps in the country.On Wednesday at least 53 migrants were killed when a detention centre in Tripoli was hit by an air strike. In May at least 65 people drowned when their boat set off from Libya and sunk off the Tunisian coast.