"Those who escaped told us there were 130 at the start, and there were around 40 dead whom they threw overboard," Senegalese police spokesman Colonel Alioune Ndiaye told Radio France International (RFI) in comments broadcast on Tuesday.

Many of the victims died of hunger and thirst after they ran out of food and water during 12 days at sea, while others fell sick, Ndiaye told RFI.

"They only survived because the captain decided to turn back and they hit the Senegalese coast. If not, they would all have died there," he said.

The boat, which ran aground at Yoff in the outskirts of the Senegalese capital Dakar, is just one of scores of wooden fishing vessels which attempt the perilous crossing to the Spanish Canary Islands each year.

Thousands of West Africans have died in a desperate attempt to escape one of the world's poorest regions and build a better life in Europe. Recent weeks have seen a rise in departures from the African coast due to a seasonal improvement in weather conditions.

People traffickers often charge thousands of dollars per migrant and fail to equip the boats with navigation devices, reliable motors or enough fuel.