The boats were heavily overcrowded with immigrants

The 208 immigrants were travelling in four boats and trying to reach the Canary Islands from Mauritania.

Spanish police say Mauritania has become a new start point for journeys to Spanish territory since Morocco increased security along its shores.

There are fears that 10,000 Africans may have gathered in Western Sahara and Mauritania to try to make the journey.

Perilous voyage

Just over a week ago, 45 African migrants trying to reach Europe drowned in separate incidents, the Mauritanian Red Crescent says.

At least 23 people drowned in rough seas after their boat collided with a Moroccan vessel coming to its aid off the Mauritanian city of Nouadhibou.

In the second incident, another 22 drowned after their boat capsized.

Thousands of Africans risk hazardous journeys to Europe each year to escape poverty, but many die in the attempt.

Since 10 November 2005 at least 1,200 people have died trying to make the trip, the Mauritanian Red Crescent says.