At least six migrants were confirmed to have died and many more are reported to be missing after their boats sank in separate incidents in the Mediterranean Sea on Saturday.

The German aid group ResQship told the Agence France-Presse news service that at least two migrants died and 20 others were missing after their small boat sank between Tunisia and Italy on Saturday.

In another incident, four people died and at least 23 were missing after their vessel sank off the Tunisian coast as they tried to cross the sea to Italy, the Reuters news agency reported. An official for the prosecutor's office of the Tunisian coastal port city of Sfax said the coast guard had rescued 53 from the boat.

ResQship said its ship, the Nadir, rescued 22 people and took them to the Italian island of Lampedusa.

Stefen Seyfert of ResQship said around 40 migrants were on the boat when it left Sfax. He said that when the Nadir arrived at the scene of the wreck, the migrants had already been in the water for about two hours.

The migrants are understood to have paid 3,000 Tunisian dinars ($980) each for the journey, according to Italian news agency ANSA.

In a social media post, ResQship said: "This is an unspeakable tragedy that could, and should, have been prevented by a humanitarian approach to migration instead of barb-wiring the European borders."

AFP reported that in the last few days alone, "thousands" of migrants have landed on Lampedusa, which is about 150 kilometers from the Tunisian coast.

There has been a sharp rise in the numbers of migrants trying to depart from Tunisia, which is struggling amid a financial crisis.

Dozens of people have gone missing or died in drowning accidents off the Tunisian coast in recent weeks, and data from the Tunisian Forum for Economic and Social Rights shows 132 migrants have died or disappeared in the first three months of this year while trying to reach Europe, reported the Associated Press news agency.

According to official data from the Italian interior ministry, more than 14,000 migrants have arrived in Italy since the beginning of the year. This compares to some 5,300 that arrived during the same period last year.

Italian Prime Minister Giorgia Meloni last week said more migrants would arrive in Italy from Africa if financial stability in Tunisia is not "safeguarded", reported Reuters. She called on the International Monetary Fund and other countries to quickly help Tunisia to "avoid a financial collapse".

The Tunisian foreign minister, Nabil Ammar, was quoted as saying the country needs more funding to better protect its borders. He said existing equipment was outdated and insufficient.

Tunisia faces a full-blown balance of payments crisis as foreign loan repayments are due later this year, reported Reuters. Tunisia's President Kais Saied last week rejected terms of a delayed $1.9 billion IMF bailout package.