Four people have died and at least 23 were missing on Saturday after their boat sank off Tunisia as they tried to cross the Mediterranean to Italy, amid a sharp rise in boats setting off from the north African country.

The coast guard rescued 53 other people from the same boat off the southern city of Sfax, two of whom were in critical condition, said a local judge, Faouzi Masmousdi.

In recent weeks, dozens of people have gone missing and died in repeated drowning accidents off the Tunisian coast. Tunisia has taken over from Libya as a main departure point for people fleeing poverty and conflict in Africa and the Middle East in the hope of a better life in Europe.

The national guard said on Friday that more than 14,000 migrants, mostly from sub-Saharan Africa, were intercepted or rescued in the first three months of the year while trying to cross to Europe – five times more than in the same period last year.

The Italian prime minister, Giorgia Meloni, said on Friday that Europe risked seeing large numbers of migrants arriving on its shores from north Africa if financial stability in Tunisia was not safeguarded. She called on the IMF and other countries to quickly help Tunisia to avoid its collapse.

The Tunisian foreign minister, Nabil Ammar, said last week that the country needed funding and equipment to better protect its borders. Tunisia has received equipment from Italy in past years, but Ammar said it was outdated and not sufficient.