The Global Sumud Flotilla, an international convoy aiming to challenge Israel’s blockade of Gaza, said its vessels were targeted for the second night in a row this week.
On Wednesday, organisers reported that the British-flagged Alma was struck by a drone while docked in the Sidi Bou Said port off Tunisia.
Security footage released by the group showed projectiles igniting on the deck and triggering a blaze. Passengers shouted warnings as flames spread, though no one was injured.
A Portuguese-flagged boat, the Family, had been hit under similar circumstances the night before.
Tunisian officials initially rejected claims of a drone strike in that case, saying investigations were ongoing.
The flotilla accused Israel of orchestrating the incidents to disrupt its mission during ongoing military operations in Gaza. Israeli authorities have not commented.
The Global Sumud Flotilla is sailing with about 20 boats carrying humanitarian aid. It began its journey from Spain on September 1 and stopped in Tunisia before attempting to reach Gaza.
Participants come from more than 40 countries and include climate activist Greta Thunberg and former Barcelona mayor Ada Colau.
United Nations experts, including Francesca Albanese, the Special Rapporteur for Palestinian territories, expressed support for the convoy.
They warned that obstructing the mission could breach international law and humanitarian norms.
The initiative is part of wider efforts by the Freedom Flotilla Coalition, which has organised similar missions since 2010. Earlier this year, its vessel Madleen carried supplies in another attempt to deliver aid to Gaza.