The Office of the United Nations High Commissioner for Refugees said in a statement more than 80 were feared drowned.

Tunisian fishermen rescued four people but one later died in hospital, according to the United Nations agency.

“The status quo cannot continue,” Vincent Cochetel, the agency’s special envoy for the Mediterranean, said in a statement.

“Nobody puts their lives and the lives of their families at risk on these desperate boat journeys unless they feel they have no other choice,” Mr. Cochetel said. “We need to provide people with meaningful alternatives that stops them from needing to step foot on a boat in the first place.”

At least 65 migrants heading for Europe from Libya drowned last May when their boat capsized off Tunisia.

Libya’s west coast is a main departure point for African migrants hoping to reach Europe, though the numbers have dropped because of an Italian-led effort to disrupt smuggling networks and support the Libyan coast guard. Although the fighting in Libya has made the situation more difficult for people-smugglers, international aid officials have warned that it could also prompt more Libyans to flee their country.

Libyans who are picked up by the country’s coast guard are routinely brought back to Libya and detained. The United Nations has pleaded with Libya’s government to free the detainees, some of whom have been locked up for years.

In May, 108 migrants and refugees were sent to the Tajoura detention center near Tripoli, which was hit by airstrikes on Tuesday night, killing at least 53 people.