Three refugee boats with over 300 people on board have gone missing in the sea between Africa and Spain's Canary Islands, with 86 migrants later rescued on Monday.
It is unclear if the 86 come from the missing boats.
Spain's Sea Rescue service tweeted on Monday that a vessel set off from Gran Canaria to pick up those stranded after a search plane spotted the refugee boat 140 kilometres south of the island.
A container ship registered in Panama was close to the migrant boat and took the passengers on board before the rescue service arrived.
"We do not yet know for sure if it is one of the missing boats. But the size and number of people on board is consistent with the information we have," a Sea Rescue spokeswoman said.
Spanish aid agency Caminando Fronteras had reported on June 23 that two boats with 60 people each had left Senegal for the Canaries.
Four days later, a third boat with 200 migrants also set off from the west African coast.
The aid agency has been in contact with relatives, who said they had not heard from their loved ones.
Helena Maleno from Caminando Fronteras told dpa: "We are very worried because after the unrest in Senegal in June and because of political persecution, people are even less prepared than usual to flee in a hurry."
All ships in the area in question were alerted days ago to keep a lookout for the migrants. The Spanish police also informed the Moroccan authorities, but the Spanish Sea Rescue spokeswoman could not say whether they had also launched a search operation.
Maleno criticized Spain for only using one search plane, which was only in the air for a few hours per day.
"If 300 Germans were missing in the Atlantic, there would be a huge search operation," she added.
Many migrants leaving Africa use the Mediterranean route to prosperous Europe via the likes of Libya and Italy. But some choose to make the 1,700 km voyage through the Atlantic from West Africa to the Spanish Canary Islands.
The ocean has much stronger currents and waves compared to the Mediterranean and is one of the most dangerous migrant routes.
According to the UN refugee agency the UNHCR, 7,278 migrants from Africa have been counted on the Canary Islands this year up to July 2.
Caminando Fronteras say at least 778 people have already died on the Atlantic route in the first half of the year. However, the number of unreported cases is probably higher.
In June, 19 boats with refugees from Senegal arrived on the Canary Islands, but not one has been officially registered since the beginning of the year.
