A migrant has been rescued, and 50 others are feared drowned after a boat sank in the Mediterranean, officials said on Sunday.

The man had been in the sea for 24 hours and said he believed everyone else on the vessel had died, according to the Alarm Phone group, which runs an emergency hotline for migrants.

The boat had come from Tunisia, it added, a common departure point for migrants risking the dangerous journey to reach Europe.

The man was rescued by a merchant ship off Tunisia and brought to Malta for medical treatment, Malta's armed forces said. They and Alarm Phone did not say when the man was rescued.