Several refugees have been found dead, and around 40 rescued from a boat off Cape Verde, authorities said, with fears dozens more may have died.

Cape Verdean media reported on Tuesday that the "pirogue" style boat common in the region left Senegal a month ago, while police said about 100 people had set off from the West African coast.

Senegal's Foreign Ministry said late on Tuesday that 38 people, including a citizen of Guinea-Bissau, were rescued from the refugee boat off the Cape Verde coast.

The vessel was spotted on Monday over 320 kilometres from the island of Sal by a Spanish fishing boat, which alerted Cape Verde authorities, police said.

"We must open our arms and welcome the living and bury the dead with dignity," said Cape Verdean Health Minister Filomena Goncalves, as quoted by the Inforpress news agency.

Around 40 survivors and several dead bodies were found on the boat, but sources differed on the exact number.

The coast guard said the total number of survivors and dead was 48.

The local morgue said it had received seven dead bodies.

Jose Rui Moreira, a health official on the island of Sal, said there were 38 survivors and seven needed to be taken to the hospital.

Thousands flee every year

Cape Verde 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.

Thousands of refugees fleeing poverty and war risk their lives to make the dangerous crossing each year.

They often travel in modest boats or motorised canoes supplied by smugglers, who charge a fee for the journey.

In January, rescue teams in Cape Verde saved around 90 refugees adrift in a canoe, while two others aboard died.

The refugees were from Senegal, The Gambia, Guinea-Bissau and Sierra Leone.