The blast Tuesday hit the beach in front of Mitiga airport in the east of the Libyan capital, the ministry statement said.
An Interior Ministry source said there were clashes Tuesday inside the airport perimeter between security forces and an “outlawed” group. The airport was badly damaged during fighting between rival militias in mid-2014.
The source, speaking on condition of anonymity, however could not say whether the attack on the civilians was intentional.
Libya has been wracked by chaos since the 2011 uprising that toppled and killed longtime dictator Muammar Gaddafi, with rival authorities and militias battling for control of the oil-rich country.
The North African country has rival administrations, with the authorities in the east not recognizing the UN-backed Government of National Accord (GNA) based in the capital.