Irish activists detained after Israeli forces illegally intercepted a Gaza-bound flotilla in international waters have described a campaign of intimidation, violence and deprivation against them.

The Global Sumud Flotilla is an international activist initiative that organises maritime missions to challenge the blockade of Gaza and deliver humanitarian aid to the Palestinian people.

Catriona Graham, one of several Irish citizens on board the latest flotilla, said she was “grabbed by the hair and cable-tied” after Israeli naval commandos hijacked the vessels and seized those on board. She described being “manhandled and left for 24 hours without adequate food or water,” after what she initially believed was an approach by the Greek coastguard turned out to be an Israeli operation.

Her account is among the most detailed to emerge amid a virtual blackout on the situation in the mainstream media. Passengers, she said, had their life jackets removed and were all cable-tied, had their shirts and jackets removed, were left “cold and uncomfortable,” and “forced into a stress position when transferred to the prison boat.”

They were provided with limited water and food, with abductees “forced to huddle together for warmth on foam mattresses.”

Catriona also said six activists were separated from the group for hours. “It took roughly 24 hours before the others knew whether they were safe,” she said, adding that she herself was “forced into a stress position” after refusing to comply without information.

Catriona’s testimony is echoed by 75-year-old Clare man Martin Guilfoyle, 75, who said he had “a gun put in my face” when Israeli forces boarded.

“There were guns everywhere, they were shouting … you don’t know what orders they are giving out,” he said. “I felt calm in myself, but I was bricking it as well because I didn’t know what was coming next.”

Guilfoyle said detainees were ordered to sit with “hands on your head,” adding: “Even if you looked at somebody, you’d be given a shove ... It was all about intimidation, intimidation, intimidation.”

He described being roughly “shoved down” and landing hard, while others “were worse off than me.” The group, he said, was transferred between vessels and held in cramped conditions on deck.

“It’s a war crime to prevent humanitarian aid reaching a war zone… All the flotilla was trying to do is bring aid in.”

Approximately 175 activists from some 70 countries were removed from more than 50 vessels after the flotilla was intercepted off Crete. The mission had set sail from ports in France, Spain and Italy with the stated aim of breaking Israel’s blockade of Gaza and delivering supplies to the victims of the ongoing genocide.

While seven Irish citizens detained in the operation have since been released, two activists — Spanish national Saif Abu Keshek and Brazilian Thiago Avila — remain in Israeli custody after a court extended their detention. A legal group representing them said both men alleged “severe physical abuse amounting to torture,” including being “beaten and held in isolation and blindfolded for days at sea.” Avila has described how he was “dragged face-down across the floor and beaten so severely that he passed out twice.”

Sinn Féin MEP Kathleen Funchion said the raids were “further evidence… that Israel is a rogue state that is acting with impunity,” adding: “Detention of the crews of these ships is utterly illegal… This cannot be tolerated.”

Sinn Féin’s foreign affairs spokesperson Donnchadh Ó Laoghaire described the incident as “another flagrant breach of international law”.

“It is appalling that hundreds of activists have been kidnapped, including seven Irish citizens,” he said.

“The Irish Government must act and intervene immediately and do all they can to ensure that Irish citizens are protected and safeguarded.

“I have written to the Minister for Foreign Affairs today, urging the Government to condemn in the strongest terms the actions of the Israeli Government. The Government must take decisive action and hold Israel to account for its blatant disregard of human rights. It is vital that we see accountability and action.

“I am calling on the Irish Government to demand the immediate release of all civilians detained, to seek urgent clarification on their whereabouts and welfare, and to work with other countries to ensure real consequences for these breaches of international law.

“This includes, but is not limited to, the passing of the Occupied Territories Bill and the immediate scrapping of the EU-Israel Trade Agreement.”