Four Tunisian migrants died and 21 others were rescued after their boat sank while trying to reach the Italian coast, a judicial source said on Wednesday.

The boat capsized after leaving Sfax in eastern Tunisia on Tuesday, court spokesman Faouzi Masmoudi told AFP, noting that an investigation had been opened.

Sfax has become a major hub for migrants from Tunisia and other parts of Africa attempting perilous voyages across the Mediterranean, often in rickety boats, in hopes of a better life.

The eastern Tunisian port city is located about 130 kilometres (80 miles) from the Italian island of Lampedusa.

Four passengers -- a woman and three children -- perished in the shipwreck, while the 21 others, all Tunisians, were rescued by the coastguard.

Tunisians have opted for the perilous sea journey in growing numbers as the country faces a grinding economic crisis and severe shortages of basic staples.

The country has also been shaken by major political tensions since President Kais Saied launched a power grab in July 2021 in what his opponents call a "coup".