The earlier alleged attack struck a boat carrying the GSF’s steering committee, which includes climate activist Greta Thunberg, as well as two Australians and occurred while it was anchored about 80km from the port of Sidi Bou Said in Tunisia.

The GSF said the attack occurred while the vessel was anchored about 80km from the port of Sidi Bou Said in Tunisia. Source: AAP / EPA / Mohamed Messara

The GSF said the Portuguese-flagged boat sustained fire damage to its main deck and below-deck storage, but all six passengers and crew were safe.

Another video shared on the GSF’s social media pages shows crew members looking up and jumping back before a flash of light and sound of an explosion is heard.

Reports of a drone are “completely unfounded”, the national guard said in a statement on its official Facebook page, suggesting that the fire may have been caused by a cigarette.

Pro-Palestinian supporters in Tunisia gathered to protest the alleged attack. Source: AAP / EPA / Mohamed Messara

Saif Abukeshek, a spokesperson for the GSF, blamed Israel for the attack.

The boat was carrying Australians Dr Bianca Webb-Pullman and Yusuf Omar. A statement from the families of Australians involved in the flotilla said: “While not physically injured, the traumatisation of a drone attack causing fire on a boat at sea is both serious, and illegal”

The blockade has remained in place through the current war, which began when Hamas attacked southern Israel in October 2023, killing 1,200 and taking about 250 hostages, according to Israeli tallies.