Seventeen people were found dead Monday on a boat drifting off El Hierro in Spain's Canary Islands, the country's maritime service said, as migrant arrivals to the archipelago surge despite the deadly dangers of the crossing. 

A Spanish military helicopter airlifted three survivors to a hospital on El Hierro, one of the smallest of the Canary Islands, a spokeswoman for the service said. "The three had hypothermia but were otherwise in good shape," she told AFP. A Spanish air force plane first spotted the boat some 265 nautical miles southeast of the island of El Hierro on Monday morning and a search and rescue vessel was deployed to the area.

The migrants on the boat were all sub-Saharan Africans, the spokeswoman said. It was not immediately clear where the boat had embarked from. Earlier this month four people were found dead in a makeshift boat that was found south of El Hierro, with 23 migrants on board. At its shortest, the sea crossing to the Atlantic islands from the Moroccan coast is around 100 kilometres (60 miles), but it is a notoriously dangerous route because of strong currents. Vessels are also typically overcrowded and in poor condition.

Migrant arrivals on the archipelago surged after increased patrols along Europe's southern coast dramatically reduced crossings to the continent via the Mediterranean. Some 3,400 people arrived in the Canaries between January 1 and March 31 this year, compared with less than half that number over the same period in 2020.  

Rights groups have warned that the Covid-19 crisis has spurred the flight effect, with those working in tourism, fishing or other casual jobs in north Africa choosing to cross the Atlantic -- or helping others do so with their boats after being left penniless by the economic meltdown triggered by the pandemic.  Last year, 1,851 people died on the route, according to the Caminando Fronteras organisation which monitors migrant flows. The founder of the NGO, Helena Maleno, tweeted that in the last month "at least" 283 people have disappeared while making their way to the Canaries on five different boats from Mauritania.

Meanwhile, around 100 migrants tried to swim to the Spanish enclave of Ceuta from neighbouring Morocco on Sunday, Spanish police said. The migrants, including minors, set off in groups of 20 to 30 throughout the day, a spokesman for the Guardia Civil police force in Ceuta said.

A handful managed to reach a beach in Ceuta on their own but most had to be rescued by Spanish rescue boats, he added.  "It is not normal -- there can be groups of three, four or five, but not this many," the police spokesman said. Ceuta, together with a second Spanish enclave in north Africa, Melilla, have the European Union's only land borders with Africa, making them popular entry points for migrants seeking a better life in Europe.