Rescue teams out in force on Wednesday in the Mediterranean as they tried to save some 88 people, including children and babies, who have been shipwrecked on a flimsy boat that gave way.
The Open arms vessel said it recovered five bodies and that the rickety boat collapsed and tipped them into the sea.
The Spanish NGO managed to distribute waistcoats and masks in the moments before the ground sank.
It is the second migrant boat that the organisation's vessel has rescued in less than 24 hours.
Several miles away it was a similar situation but on a different boat. Some 13 people drowned off the Libyan coast while it managed to save 85 who were adrift and in danger of sinking in international waters.
Their boat was badly damaged, with water and gasoline spilled inside.
The NGO has criticised the fact that the countries of the Mediterranean have abandoned these people and have not moved government relief teams.
Since the start of the year, more than 575 migrants have died while trying to reach Europe, according to the UN's Migration body the IOM.
The rescue ship set sail from the port of Barcelona (northeast Spain) on November 4 bound for the central Mediterranean, where in recent days it was waiting to receive a request for help.