The head of the UN refugee agency on Sunday called on European countries to apply their generosity towards Ukrainian refugees to others as well as 90 more people died in a fresh "tragedy" in the Mediterranean Sea.

"More than 90 people have died in another Mediterranean tragedy," Filippo Grandi said on Twitter.

"Europe has proven its ability to host 4 million refugees from Ukraine generously and effectively," Grandi said. "It must now urgently consider how to apply this to other refugees and migrants knocking, in distress, at its doors."

Grandi re-tweeted earlier remarks from the French medical charity Medecins Sans Frontieres, which said on Twitter that over 90 people died in international waters after leaving from Libya "on an overcrowded boat many days ago."

"The commercial tanker Alegria 1 rescued the only 4 survivors early this morning. We know from our initial contact with Alegria 1 that the survivors reported being at sea for at least four days on a boat with nearly 100 people on board," the charity said.

These people need urgent protection, the agency said, urging Italy and Malta "to assume coordination of such an operation and assign a place of safety for the survivors before it is too late."

For years, North African countries such as Tunisia, Algeria, Libya, Mauritania, and Morocco have witnessed attempts by migrants from mainly sub-Saharan Africa to reach Europe, hoping for a better life.

While some of the migrants manage to reach their destination, others often die during the journey. (Anadolu Ageny)

•Mediterranean boat tragedy: A commercial tanker rescued four people from a life raft. (Representational)