At least 58 migrants drowned as their boat sank near the Mauritanian coast after a week at sea, the International Organization for Migration said on Thursday.
The UN agency said another 83 people swam to shore, while survivors said at least 150 people including women and children were aboard the vessel, which had set sail from The Gambia on November 27.
They said the boat was running low on fuel as it was nearing the coast of the northwestern African nation.
"The Mauritanian authorities are very efficiently coordinating the response with the agencies currently present in Nouadhibou," said Laura Lungarotti, IOM's chief of mission in Mauritania.
"Our common priority is to take care of all those who survived and bring them the support they need," she added.
The injured are being treated in hospital in Nouadhibou, Mauritania's westernmost town on the Atlantic coast, the IOM statement said.
Mauritanian authorities are in contact with Gambian consular services "to ensure that the necessary support is provided to the migrants", the statement said.
The Gambian ambassador to Mauritania is headed to Nouadhibou, it added.
Agence France-Presse