A boat found drifting off the coast of Spain's Canary Islands with the bodies of 17 migrants on board will be towed on Tuesday to one of the archipelago’s islands, officials said.

A Spanish maritime rescue vessel was heading to the area where the boat was spotted on Monday morning some 500 kilometres (300 miles) southeast of the island of El Hierro, the office of the central government's representative on the archipelago said.

It will then tow the migrant boat to the port of Los Cristianos on the island of Tenerife, a journey that is expected to take 48 hours, the office added in a statement.

A Spanish military helicopter on Monday airlifted three survivors -- two men and a woman -- from the migrant boat to a hospital on the island of Tenerife

One of the men was in serious condition with "severe dehydration", emergency services tweeted.

The migrants on the boat were all sub-Saharan Africans.

Separately, Spain's maritime rescue service on Tuesday picked up 41 migrants, including nine women and three children, who were found on a boat some 170 nautical miles south of the island of Gran Canaria.

The migrants, who are in goold health, are expected to arrive in the port of Los Cristianos on Tuesday evening.

Migrant arrivals on the Atlantic archipelago surged after increased patrols along Europe's southern coast dramatically reduced crossings to the continent via the Mediterranean

At its shortest, the sea crossing to the Atlantic islands from the Moroccan coast is around 100 kilometres (62 miles) , but it is a notoriously dangerous route because of strong currents. Vessels are also typically overcrowded and in poor condition.

Last year, 1,851 people died on the route, according to the Caminando Fronteras organisation which monitors migrant flows.