A Moroccan official says at least 21 migrants have been rescued at sea by the Royal Marines after their rubber dinghy floundered.

The official said he couldn't confirm a report by an NGO based in northern Morocco that 45 migrants had drowned. He said he knew of only one body being recovered Thursday, a day after the boat went adrift as it crossed the Mediterranean Sea.

The official, who has information about the incident, wasn't authorized to discuss it and asked to remain anonymous. He said the migrants, all sub-Saharans, were in a critical state when pulled from the water north of Nador.

Spanish human rights activist Helena Maleno, who runs a Tangiers-based NGO, said 45 migrants died. She said she based her figure on accounts from seven female survivors.