Tunisian authorities have denied claims that one of the Gaza-bound vessels carrying aid and pro-Palestinian activists including Greta Thunberg was attacked by a drone.

The organisers of the flotilla, Global Sumud Flotilla (GSF), said that the Portuguese-flagged vessel had been struck by a drone while anchored outside the port of Sidi Bou Said in Tunisia. All six passengers and crew were safe, they added.

A spokesperson for Tunisia’s national guard told the Agence France-Presse news agency that “no drone” had been detected and the investigation was ongoing.

The humanitarian aid flotilla set sail from Barcelona last week, and arrived in Tunisia on Sunday.

The GSF said their “Family boat” was struck in Tunisian waters, and fire had damaged the main deck.

In a series of videos published to their Instagram, spokespeople for the GSF said an “incendiary device” caused a fire onboard the vessel, which the crew was able to extinguish.

Tunisia’s National Guard spokesman told Mosaique FM radio that reports of a drone attack on the flotilla “have no basis in truth”, Reuters reported.

He added that an initial inspection indicated the explosion originated inside the vessel.

UN Human Rights Council special rapporteur and Tunisian resident Francesca Albanese, who was also featured in videos shared by the GSF, said that if an attack could be verified it would be an “assault and aggression against Tunisia, and Tunisian sovereignty”.

In a post to ‘X’, she said she was at Sidi Bou Said port and “trying to figure out the facts with local authorities”.

Albanese has been a prominent critic of Israel’s military offensive in Gaza, and has been subject to sanctions imposed by the US in July – a decision welcomed by Israeli Prime Minister Benjamin Netanyahu who called them a “firm measure against the mendacious smear campaign” against Israel.

Flotilla organisers have said that the aim of their mission is to “break Israel’s illegal siege on Gaza”, but have faced several setbacks.

In June, Israeli forces boarded a boat carrying humanitarian aid to Gaza and detained the 12 activists onboard, including Swedish activist Thunberg.

Israeli authorities escorted the activists to the port of Ashdod before deporting them from the country.

Israeli authorities have characterised the attempts to sail aid to Gaza as publicity stunts that offered no real humanitarian assistance.

There have also been prior allegations of drone attacks on aid ships bound for Gaza; the Freedom Flotilla alleged that its ship The Conscience was struck by a drone in May off the coast of Malta.

The BBC was sent a recording of the distress call from the flotilla ship, recorded by a crew member on a nearby oil tanker. The captain of the flotilla ship can be heard reporting drone strikes and a fire onboard.

The Maltese government said everyone aboard the ship was “confirmed safe” and that a fire onboard the ship was “brought under control overnight”.

Last month a UN-backed body confirmed that there was famine in Gaza and the UN’s humanitarian chief said it was the direct result of Israel’s “systematic obstruction” of aid entering Gaza.

The report was labelled an “outright lie” by Israel, which has denied there is starvation in the territory.

In March, it introduced a nearly three-month total blockade on supplies entering the Strip, claiming the aid was being taken by Hamas.

It started allowing a limited amount of aid back into the territory after increasing international pressure.

Israel has since tried to impose its own distribution system through the controversial Gaza Humanitarian Foundation, which has been criticised by aid agencies.

In 2010, Israeli commandos killed 10 people when they boarded Turkish ship Mavi Marmara which was leading an aid flotilla towards Gaza.

The Israeli military launched a campaign in Gaza in response to the Hamas-led attack on 7 October 2023, in which about 1,200 people were killed and 251 others were taken hostage.

At least 64,522 people have been killed in Israeli attacks in Gaza since then, according to the territory’s Hamas-run health ministry.