Activists from the Freedom Flotilla Coalition (FFC) had set out to protest against Israel’s military campaign in the Gaza Strip and its restrictions on the entry of humanitarian aid.
Israel’s military used drones to drop a “white irritant substance” on the Gaza-bound aid boat before boarding and detaining the activists near Egypt.
Pictures from the yacht showed the deck covered in white liquid, which had been sprayed from a drone, according to the group behind the mission. It was not immediately clear what the liquid was.
The boat was later pictured approaching the Port of Ashdod and Thunberg was pictured ashore.
Huwaida Arraf, the co-founder of the International Solidarity Movement, told Al Jazeera that crew members had reported that their eyes were burning after drones dropped an unknown substance.
“They had two drones hovering above them that dropped some kind of chemical on the vessel. We don’t know what that chemical was. Some people reported that their eyes were burning.”
Israel did not confirm what the white substance was.
Andrew Fox, a former British paratrooper, said: “Based on what we can see in the images, this may be a water-based irritant such as ‘skunk water’ used to disrupt co-ordination and impair senses”.
Invented by Israeli firm Odortec, skunk water was first used by the military against demonstrators in the occupied West Bank in 2008. Since then, the IDF has continued to spray the pungent liquid on protesters.
“It is extremely unlikely to be anything more damaging, such as white phosphorus, as this would leave burn marks,” he added.
Fox also pointed to the possibility that it could be illumination paint, used to mark vessels at night. This helps the military keep track of the vessel and gives soldiers a better target to aim at.
The FFC said the activists were “kidnapped by Israeli forces” while trying to deliver aid to the territory.
“The ship was unlawfully boarded, its unarmed civilian crew abducted, and its life-saving cargo – including baby formula, food, and medical supplies – confiscated,” it said in a statement.
David Mencer, an Israeli Government spokesman, said that the yacht was carrying a “meagre” amount of aid, which he said “of course will be sent into Gaza”.
“To poor Greta, we say, who is really feeding Gaza and who is feeding their own ego?” Mencer said, adding that the crew would be deported back to their home countries.
Sweden’s Foreign Ministry said it was in contact with Israeli authorities and said it would help Thunberg “resolve her situation”.
President Emmanuel Macron requested that French nationals aboard the boat “be allowed to return to France as soon as possible”, his presidential office said.
Israel’s Foreign Ministry portrayed the voyage as a public relations stunt, saying in a post on X that “the ‘selfie yacht’ of the ‘celebrities” is safely making its way to the shores of Israel”.
“The show is over,” it added.
Footage showed Israeli military personnel handing sandwiches and water to the activists, who were wearing orange life vests.
Thunberg, 22, a prominent climate campaigner, was joined by other pro-Gaza activists including Liam Cunningham, the Game of Thrones actor, and Rima Hassan, a European parliamentarian.
The Israeli Government had vowed to prevent the “unauthorised” ship from breaching the naval blockade of Gaza, urging it to turn back.
Ms Thunberg said in a pre-recorded message released by the coalition after the ship was halted: “If you see this video, we have been intercepted and kidnapped in international waters”.
Hamas has condemned their detention, calling it an “attack on civilian volunteers acting out of humanitarian motives”.
Francesca Albanese, the United Nations special rapporteur on human rights in the Palestinian territories, called on Israel to release the activists “immediately” and urged boats across the Mediterranean to sail to Gaza in solidarity. “They shall sail together – united, they will be unstoppable,” she wrote on X.
Thunberg had departed Sicily a week ago on the boat. Along the way, it rescued four migrants who had jumped overboard to avoid being detained by the Libyan coastguard.
Israel is facing mounting international pressure to allow more aid into Gaza, which the UN has called “the hungriest place on Earth” following the two-and-half-month aid blockade aimed at pressuring Hamas.
More than 600 days of war and an 11-week Israeli blockade of all aid has pushed more than two million people in Gaza towards famine.
