Dozens of migrants trying to reach Europe drowned in the Mediterranean on Friday and 100 more were sent back to Libya, the United Nations said, while Italian authorities signalling opposition to more migration from Africa seized a rescue ship.

The UN refugee agency UNHCR said 65 people drowned when their boat capsized off Tunisia, and 101 others who had been picked up at sea were returned to Libya, despite repeated warnings that it is not a safe country to send people back to.

It was one the deadliest shipwrecks involving migrants trying to reach Europe via north Africa this year.

Tripoli, a hub for migrants and refugees hoping to sail to Europe after a perilous trek through the Sahara, has long been a dangerous dead end: Many end up in detention centres or being tortured by their captors while money is extorted from their families, according to UNHCR.

But it has become even more dangerous since forces loyal to Khalifa Haftar began an offensive a month ago on the capital,triggering renewed warfare between rival Libyan factions.

Haftar is an “aspiring military dictator” planning a”Gadhafi-style military dictatorship”, according to an op-ed in Friday’s Wall Street Journal by Libya’s internationallyr ecognised Prime Minister Fayez Serraj.

Jan Egeland, head of the Norwegian Refugee Council, told Reuters that the international community needed to stabilise Libya and the sub-Saharan countries producing flows of migrants, and stop “fuelling the fire by giving generals hope that they can take over”.

Europeans bore part of the responsibility to avoid the “mass haemorrhage of human lives in the Mediterranean,” he said.