TUNIS, TUNISIA -- About 20 African migrants were found dead Thursday after their smuggling boat sank in the Mediterranean Sea while trying to reach Europe, Tunisian authorities said. Five survivors were rescued and the Tunisian navy is searching for up to 20 others still believed missing.

Tunisian coast guard boats and local fishermen found and retrieved the bodies in the waters off the coastal city of Sfax in central Tunisia, Defence Ministry spokesman Mohamed Ben Zekri told The Associated Press.

According to survivors, the migrant smuggling boat was carrying about 40 or 50 people heading toward Italy, Ben Zekri said.

The boat was overloaded and in poor condition, and faced strong winds Thursday morning that may have contributed to the sinking, said National Guard spokesman Ali Ayari. It was carrying migrants from sub-Saharan Africa, he told The AP.

Tunisian navy units were searching for any more survivors.

Tunisian authorities say they have intercepted several migrant smuggling boats recently but that the number of attempts has been growing, notably between the Sfax region and the Italian island of Lampedusa.

More than 1,100 migrants have died or disappeared in the Mediterranean this year, according to estimates from the International Organization for Migration.

Migrant smuggling boats frequently leave from the coast of Tunisia and neighbouring Libya carrying people from across Africa, including a growing number of Tunisians fleeing prolonged economic difficulties in their country.

Tunisians have made up the vast majority of migrants arriving in Italy this year, despite efforts by Rome to negotiate with Tunis to put a stop to the crossings. Of the 34,001 migrants who had arrived in Italy so far this year, 12,847 were Tunisian, or 38%. Bangladeshis were the next biggest group, followed by those from Ivory Coast, Algeria, Pakistan and Egypt.

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Nicole Winfield in Rome contributed.