Sixty-three people are believed to have died after a refugee boat from Senegal was found off West Africa's Cabo Verde islands, the International Organization for Migration (IOM) said.

The 38 survivors included four children aged 12 to 16, IOM spokesperson Safa Msehli told AFP news agency on Wednesday.

The long wooden fishing vessel, known as a pirogue, was spotted on Monday in the Atlantic Ocean about 277 nautical kilometres from the Cape Verdean island of Sal, police said.

The Spanish fishing vessel that saw it alerted Cabo Verdean authorities.

The Cabo Verde archipelago lies about 600 kilometres off the coast of West Africa on the maritime migration route to the Spanish Canary Islands – a gateway to the European Union.

Emergency services recovered the remains of seven people, Msehli told AFP news agency, while another 56 people are believed to be missing.

"Generally, when people are reported missing following a shipwreck, they are presumed dead," she said.

The boat left the Senegalese fishing village of Fasse Boye on July 10 with 101 people on board, Senegal's Foreign Ministry said on Tuesday, citing survivors.

Apart from one person from Guinea-Bissau, they were all Senegalese. The authorities have not, for the moment, said what happened to the boat once it set off.

But Abdou Karim Sarr, an officer with the local fisherman's association the CLPA, told AFP: "Those missing are all dead."

Dangerous route

Moda Samb, a local elected official from Fasse Boye, said nearly all those on the boat had grown up in this fishing community.

"One of the survivors who had his father on the telephone told him that the others were dead," he said.

Other families were still waiting to hear if their children were among the survivors, he added.

The authorities in Cabo Verde said they had mobilised the necessary resources to care for the survivors, seven of whom had to be hospitalised after reaching Sal on Tuesday.

Senegal's Foreign Ministry said it would be working to repatriate its citizens as soon as possible.

Senegal has already dealt with several similar tragedies in recent years.

Cabo Verde lies on one of the maritime migration routes used by thousands of Africans fleeing poverty and war towards Europe.

Many of them aim to reach the Spanish Canary Islands, one of the most dangerous routes, often travelling in the pirogue boats, which are vulnerable to the vagaries of the weather.

Around 90 refugees from Senegal, Gambia, Guinea-Bissau and Sierra Leone had to be rescued in the seas off Cape Verde in January this year.

At least 559 people died attempting to reach the Canary Islands in 2022, while 126 people died or went missing on the same route in the first six months of this year, with 15 shipwrecks recorded, according to the IOM.