The Global Sumud Flotilla, an international activist stunt, said on Wednesday that one of its boats was attacked by a drone at a Tunisian port, the second such strike in two days, and the third such accusation by a Greta Thunberg-associated group this year.
The GSF, which claims it is seeking to break Israel's naval blockade and deliver humanitarian aid to war-torn Gaza using civilian boats, said in a statement that all passengers and crew were unharmed.
GSF reported the first attack on Tuesday, saying one of its vessels had been struck by a drone in Tunisian waters at the Sidi Bou Said port, reports Tunisian authorities said were false.
A Tunisian Coast Guard spokesperson did not respond to a call from Reuters on Wednesday.
One of the flotilla's organisers accused Israel of carrying out the attack.
"Israel continues to breach international law and terrorise us. We will sail to break the blockade on Gaza no matter what they do," Saif Abukeshek, a member of the GSF steering committee, told Reuters.
The Israeli military did not immediately respond to a request for comment.
In June, Israeli naval forces boarded and seized a British-flagged yacht carrying Thunberg, among others. Israel dismissed the aid ship as a propaganda stunt in support of Hamas.
Before the raid, the group had also made unsubstantiated claims that one of its vessels was hit by a drone strike off Malta.
The flotilla posted a video on Instagram of the alleged attack, showing a luminous object hitting the boat and fire erupting on board. Reuters was not immediately able to verify the video. Comments have suggested it was possibly a flare set off incorrectly by a crewmember.
Following the strike, hundreds gathered near the port, where the flotilla's boats were located at the time of the incident, waving Palestinian flags and chanting slogans against Israel and the United States.
The group said that the British-flagged Alma sustained fire damage to its top deck and an investigation was underway.
Several ambulances rushed to the port, while a Reuters witness reported coastguard boats near the Alma.
(Reporting by Tarek Amara, Enas Alashray and Ahmed Tolba; Editing by Stephen Coates and Saad Sayeed)