Four Tunisian migrants died and 19 were missing after their boat capsized, a judicial source told AFP, the latest deadly mishap in waters off North Africa.
A total of 30 Tunisians, most of them young men, had set off in the small vessel, said Farid Ben Jha, spokesman for the Mahdia and Monastir court on the country's east coast.
One of them managed to swim to shore and raise the alarm after their boat sank at dawn off the coast of Mahdia governorate, which is only around 140 kilometres (87 miles) from the Italian island of Lampedusa.
"Seven were able to be rescued" and four bodies were found, Ben Jha said, adding that the other passengers were missing.
"The boat was too small to carry 30 people," he said.
Those rescued did not say where exactly the boat had set off from.
Four people were arrested for helping to organise the attempted sea crossing, Ben Jha added. He said an investigation had been opened to identify those responsible.
Also Sunday, the defence ministry in neighbouring Algeria said that country's coastguards had recovered four bodies from the Mediterranean Sea and rescued 13 migrants after a boat capsized in its waters.
On Tuesday the United Nations refugee agency said 15 migrants drowned after two boats capsized off Libya, adding to the toll on the perilous sea route to Europe.
Libya is a major point of departure for desperate migrants seeking to reach Europe, many of them from sub-Saharan African countries.