It was around lunchtime when the group of youngsters found the gadget in the car park.
A bomb squad was called to the spot to detonate the grenade and found it was old and unloaded of explosives.

Newspaper Jornal de Notícias said the case came to light after the car park guard spotted the children playing with an unusual-looking object and went to check what it was.
After discovering it was a potentially explosive device the guard called the GNR, who promptly set up a safety perimeter around the car park and evacuated it.
The alarm was raised at around 12.40pm and two hours later the incident had been resolved after the device was deemed to be of no risk and was removed from the spot.