Israeli forces intercepted a Gaza-bound aid flotilla and "illegally kidnapped” eight Irish citizens, including the sister of Ireland’s President Catherine Connolly, organizers said Monday.

Israeli forces intercepted the flotilla on Monday after it sailed from Türkiye last week. The Global Sumud Flotilla vessels are the latest in a string of attempts by activists to breach Israel's deadly blockade of the Palestinian territory.

Around 50 ships had departed from southwestern Türkiye on Thursday. Some 10 boats from the convoy were intercepted in international waters and boarded by Israeli forces earlier Monday.

Organizers said the interception took place around 70 nautical miles off the island of Cyprus, with at least six of the 15 Irish participants detained.

"Global Sumud Flotilla is under attack!" the group wrote on X.

"The Israeli occupation has again illegally and violently intercepted our international fleet of humanitarian vessels and abducted our volunteers."

Margaret Connolly, an Irish doctor and President Connolly's sister, was among those "illegally kidnapped" by Israel, organizers said in a statement sent to AFP.

"Eight Irish people have been illegally detained in this operation," it said.

President Connolly, on a planned trip to the UK, told reporters after talks in London with King Charles III that the news was "upsetting".

"I'm very worried about her, and I'm also very concerned about her colleagues on board," she said, adding she did not have any details.

Videos posted by the organizers on social media showed Connolly and five others which appear to have been recorded in advance of their detention.

In her video, Connolly said: "If you are watching this video, it means I have been kidnapped from my boat in the flotilla by the Israeli occupying forces".

"Her participation in this flotilla was her own decision and not related to President Connolly," organizers said.

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

Organizers said the mission included 426 participants, among them 96 Turkish activists and participants from 39 other countries, including Germany, the U.S., Argentina, Australia, Bahrain, Brazil, Algeria, Indonesia, Morocco, France, South Africa, the UK, Ireland, Spain, Italy, Canada, Egypt, Pakistan, Tunisia, Oman and New Zealand.

On April 29, Israeli forces also attacked the Global Sumud aid flotilla off the coast of the Greek island of Crete.