At least 74 migrants died in a shipwreck off the coast of Libya on Thursday, the United Nations' migration agency said, with 47 survivors brought to shore by coastguards and fishermen.
Libya, which has had no stable central government since a NATO-backed uprising in 2011, is a major transit point for mainly African migrants seeking to cross the Mediterranean and reach Europe.
At least 900 have already drowned this year attempting the crossing, according to the agency, the International Organisation for Migration (IOM).
Another 11,000 have been stopped at sea and returned to Libya, where migrants are often detained, exploited or abused.
IOM and the UN refugee agency UNHCR have both said that Libya should not be considered a safe port of return, and that migrants rescued or stopped at sea should not be taken back there.