“If you see this video, we have been intercepted and kidnapped,” Thunberg said in pre-recorded footage shared by the coalition.
Video from the group shows the activists with their hands up as Israeli forces boarded the vessel, with one of them saying nobody was injured prior to the interception.
Israel’s foreign ministry, in a post on social media, said “all the passengers of the ‘selfie yacht’ are safe and unharmed”, adding it expected the activists to return to their home countries.
Turkey condemned the interception as a “heinous attack” and Iran denounced it as “a form of piracy” in international waters.
In May, another Freedom Flotilla ship, the Conscience, reported it was struck by drones in an attack the group blamed on Israel. In 2010, an Israeli commando raid on the Turkish ship Mavi Marmara, which was part of a similar attempt to breach the naval blockade, left 10 civilians dead.
On Sunday, Defence Minister Israel Katz said the blockade, in place for years before the Israel-Hamas war, was needed to prevent Palestinian militants from importing weapons.
Journalists on board
The Madleen was intercepted about 185km west of the coast of Gaza, according to coordinates from the coalition.
President Emmanuel Macron requested that the six French nationals aboard the boat “be allowed to return to France as soon as possible”, a presidential official said.
Two of them are journalists, Omar Fayyad of Qatar-based Al Jazeera and Yanis Mhamdi who works for online publication Blast, according to media rights group Reporters Without Borders, which condemned their detention and called for their “immediate release”.
Al Jazeera “categorically denounces the Israeli incursion”, the network said in a statement, demanding the reporter’s release.
Adalah, an Israeli NGO offering legal support for the country’s Arab minority, said the activists on board the Madleen had requested its services, and that the group was likely to be taken to a detention centre before being deported.
Israel is facing mounting pressure to allow more aid into Gaza to alleviate widespread shortages of food and basic supplies.
In what organisers called a “symbolic act”, hundreds of people launched a land convoy on Monday from Tunisia with the aim of reaching Gaza.
‘Our children are dying ‘
Israel recently allowed some deliveries to resume after barring them for more than two months and began working with the newly formed, US-backed Gaza Humanitarian Foundation.
But humanitarian agencies have criticised the GHF and the United Nations refuses to work with it, citing concerns over its practices and neutrality.
Dozens of people have been killed near GHF distribution points since late May, according to Gaza’s civil defence agency.
In Gaza City on Monday, displaced Palestinian Umm Mohammed Abu Namous told AFP that she hopes “that all nations stand with us and help us, and that we receive 10 boats instead of one”.
“We are innocent people,” she said. “Our children are dying of hunger... We do not want to lose more children because of hunger.”
The Hamas attack that triggered the war resulted in the deaths of 1219 people on the Israeli side, mostly civilians, according to an AFP tally of official figures.
The health ministry in Hamas-run Gaza says at least 54,880 people, the majority civilians, have been killed in the territory since the start of the war. The UN considers these figures reliable.
Out of 251 taken hostage during the Hamas attack, 54 are still held in Gaza, including 32 the Israeli military says are dead.
-Agence France-Presse
