A major rescue operation off the Canary Islands has ended with 152 people being brought safely to El Hierro after their overcrowded cayuco was found drifting at sea, although one person on board had died.

The operation unfolded after the Maritime Rescue Coordination Centre in Tenerife received an alert just before 7.30pm yesterday (Wednesday) reporting a migrant boat south of El Hierro.

Salvamento Marítimo mobilised several resources, including the Helimer 204 rescue helicopter, Salvamar Navia and Guardamar Polimnia.

The helicopter located the cayuco at around 8.30pm, approximately 29 nautical miles southwest of El Hierro, close to the position initially reported.

Salvamar Navia subsequently reached the vessel and secured a tow at around 9.00pm, before the Guardamar Polimnia later carried out the transfer of those on board.

The operation was complicated by difficult weather and sea conditions and continued into the early hours of this morning.

Once everyone had been transferred and rescuers had confirmed that nobody remained aboard, the empty cayuco was left drifting because conditions made recovering it impractical.

The Guardamar Polimnia eventually arrived at the port of La Restinga at approximately 3.00am.

A final count established that 152 people had survived the journey, comprising 130 men and 22 women, while an adult man had died.

Fifteen of those rescued were minors.

The occupants were reported to include people from Senegal, Gambia, Guinea-Conakry, Mali and Ivory Coast, and the cayuco had reportedly departed from Bato Kunku in Gambia.

Those on board are understood to have spent around 15 days at sea, enduring strong winds and difficult conditions during the Atlantic crossing to the Canary Islands.

Emergency and humanitarian teams were waiting when the survivors reached La Restinga.

Ten people required medical attention for dehydration, hypothermia and other health problems following the prolonged voyage, while seven were transferred to the Hospital Nuestra Señora de los Reyes for further treatment.

The latest arrival again highlights the dangers of the Atlantic migration route to the Canary Islands, where vessels can spend days or even weeks at sea before reaching the archipelago or being intercepted by rescue services.

The conditions faced by those making the journey can deteriorate rapidly when vessels encounter bad weather, mechanical problems or shortages of fuel, food and drinking water.

This morning's operation involved a substantial deployment of maritime rescue resources and continued for several hours before all survivors could finally be brought safely ashore.