Around 50 migrants are feared to have drowned in waters off the Moroccan coast, the Spanish coastguard has said, APA reports quoting BBC.
Rescue services managed to retrieve three "exhausted and disorientated" men from a half-sunk rubber dinghy near Spain's Alboran Island.
It is believed many more were originally on board.
A coastguard spokeswoman said they had likely drowned, adding that rescuers were still surveying the water where the boat was found.
The survivors are aged between 17 and 25, and from sub-Saharan Africa. They have been taken to hospital in Almeria, southern Spain.
The coastguard said in a statement that the boat "had been drifting for several days after leaving the northern coast of Morocco".