Israeli forces have raided a Gaza-bound aid flotilla, with video showing numerous vessels being boarded and crews detained despite being in international waters.

The Global Sumud Flotilla, the international movement heading the mission, said Israeli military personnel boarded several boats off Cyprus on Monday, as the convoy tried to reach the besieged Gaza Strip.

“Global Sumud Flotilla is under attack!” the group wrote on social media. “The Israeli occupation has again illegally and violently intercepted our international fleet of humanitarian vessels and abducted our volunteers.”

It expressed outrage at “the normalisation of these violations of international maritime law and the kidnapping of peaceful civilians in international waters”, demanding the swift release of the activists and the blockade of Gaza ended.

Video shared by the organisers showed activists filming as Israeli forces approached and boarded the boats. Israel’s foreign ministry said on social media that it “will not allow any breach of the lawful naval blockade on Gaza”.

Organisers said the boats were intercepted 250 nautical miles (463 kilometres) from the shores of Gaza. Unlike previous interceptions, mostly under the cover of night, the Israeli military boarded the boats in daylight.

Turkiye’s foreign ministry condemned the Israeli intervention as an “act of piracy”, adding that Ankara was taking the necessary steps to ensure the safe return of Turkish citizens aboard the flotilla in coordination with other relevant countries.

Turkish President Recep Tayyip Erdogan condemned Israel’s action against the “voyagers of hope” and called on the international community to act.

More than 50 vessels sailed from the Turkish port city of Marmaris last week, in what organisers described as the final stage of a journey aimed at challenging Israel’s blockade of the Palestinian enclave.

Reporting from Gaza, Global News Insight’s Tareq Abu Azzoum said Israeli media described the operation as one of the largest naval interception campaigns targeting a Gaza-bound flotilla in recent years.

Abu Azzoum said Israeli naval forces intercepted about 20 vessels near Cyprus, far from Gaza, and reportedly detained about 100 activists.

Israeli media reported that activists were transferred to what was described as a “floating prison” before being taken to the Israeli port of Ashdod for interrogation by intelligence agents.

The sister of Irish President Catherine Connolly was among those “illegally kidnapped” by Israel, organisers said in a statement sent to AFP news agency.

President Connolly, on a planned trip to London, told reporters after talks with King Charles that it was “upsetting” to hear news that her sister and doctor Margaret Connolly was among the detained

Ireland has been among the most outspoken critics of Israel’s bombardment of Gaza, and recognised the Palestinian state in 2024.

Abu Azzoum also cited Israeli media reports saying the military had used electronic interference tactics, including broadcasting songs over radio frequencies, to disrupt communications between flotilla vessels in the Mediterranean Sea.

The interceptions came as the Turkish branch of the flotilla campaign said one of its vessels, the Munki, had come under “attack” and “close harassment” by Israeli military boats.

“The flotilla’s vessel Munki has been attacked by the occupying Israeli forces. We have currently lost contact with the vessel,” Global Sumud Turkiye said in a statement posted on X on Monday.

Bader al-Noaimi, coleader of the Global Sumud Flotilla legal team, said the vessels were in international waters when the interceptions began and accused Israel of targeting a “peaceful humanitarian flotilla”.

“Our flotilla was in international waters at the time of the start of this military aggression and operation against this peaceful humanitarian flotilla,” al-Noaimi said.

He added that the vessels were also within the search and rescue zone of Cyprus, which he said meant Cypriot authorities had a legal obligation under the United Nations Convention on the Law of the Sea to respond to distress calls.

“We have been making distress calls since the start of the attack against the flotilla,” he said, adding that the calls began about 07:20 GMT.

About an hour before the reported interceptions, Israel’s Ministry of Foreign Affairs warned the flotilla to abandon its mission.

“Change course and turn back immediately,” the ministry said in a statement.

The Israeli public broadcaster Kan earlier reported that Prime Minister Benjamin Netanyahu was expected to authorise the military to prevent the flotilla from reaching Gaza, and to capture vessels trying to breach its naval blockade.

Israel has maintained a blockade on Gaza since 2007, saying it is necessary to prevent weapons from reaching Hamas and other armed groups.

Rights groups and humanitarian organisations have repeatedly criticised the blockade, describing it as collective punishment imposed on Gaza’s population.