Greta Thunberg's captured Gaza flotilla crew has been detained in a notorious Israeli prison where guards have been accused of torturing Palestinian inmates, it is understood. It comes after IDF commandos intercepted almost all of the flotilla's 40 boats carrying aid to the Gaza Strip and took captive more than 450 foreign activists, including the 22-year-old Swedish climate campaigner.The Israeli foreign ministry said the arrested activists were in 'good health' and were making their way 'safely and peacefully to Israel', from where they will be deported to Europe in the next few days.But the Foreign Office has said it was 'very concerned' for the safety of British members of Thunberg's mission, who are understood to be incarcerated in the Ketziot prison in the Negev desert. Israel is reportedly not expected to begin deportations until Sunday or Monday, meaning activists may be in the Ketziot for multiple nights. Former Palestinian detainees have made claims about the mistreatment they experienced at the prison, including sexual abuse, severe beatings, medical negligence and being deprived of food and water.Speaking to the BBC about his experience, former Palestinian detainee Abdul Karim Mushtaha said he was threatened with castration.'They would strip us naked. They would Taser us. They would hit us in a sensitive place. They would tell us "We will castrate you",' he said. Swedish climate activist Greta Thunberg (C) and Brazilian activist Thiago Avila (R), along with other activists, after the Israeli navy intercepted the Global Sumud Flotilla carrying humanitarian aid to Gaza on October 1, 2025 In footage posted to X by the Israel Foreign Ministry, Swedish climate activist Thunberg is seen among those being detained by officials Another former inmate of the jail, Omar, said prisoners were often hit with batons by guards.'After we got tortured, I was in pain all night - from my back to my legs. The guys would carry me from my mattress to the toilet. My body, my back, my legs - my whole body was blue from beatings. For nearly two months I couldn't move,' he said.The Israeli Prison Service has previously said it is 'not aware' of the sexual abuse claim or any of the other claims made about torture at Ketziot. Israel faced international condemnation and protests on Thursday after its military intercepted Thunberg's flotilla.Cameras broadcasting live feeds from the boats showed armed Israeli soldiers in helmets and night vision goggles boarding the ships, while passengers huddled in life vests with their hands up. A video from the Israeli foreign ministry showed Thunberg, the most prominent of the passengers, sitting on a deck surrounded by soldiers.Pro-Palestinian demonstrators took to the streets in cities across Europe as well as in Karachi, Buenos Aires and Mexico City to protest Israel's capturing of the activists two years into its assault on Gaza. Italian unions called a general strike for Friday.The Global Sumud Flotilla, the organiser of the voyage, said on X that more than 450 volunteers had been detained. Earlier it said some of them were transferred to one large cargo vessel before being taken ashore. The Global Sumud Flotilla said its vessels were being boarded by military personnel, as it approached Palestinian territory, with cameras taken offline in a post on social media Thunberg and Nelson Mandela's grandson Mandla Mandela are part of the controversial convoy of around 43 boats and 500 activists and aid workers sailing on what they describe as a 'peaceful mission' to deliver supplies to Palestinians in Gaza Greta Thunberg has been hauled off her 'Freedom Flotilla' by Israeli naval forces as it neared the besieged Gaza Strip The Israel Foreign Ministry added that Thunberg will be transferred to an Israeli portOne boat, the Marinette, was 'still sailing strong,' flotilla organisers said on a live video stream that showed the crew piloting the boat. Organisers said the Marinette was about 80 nautical miles from Gaza on Thursday night, and about 10 nautical miles from where Israel began intercepting other boats in the flotilla.In a video posted to social media, Thunberg, said: 'If you are watching this video, I have been abducted and taken against my will by Israeli forces. Our humanitarian mission was non-violent and abiding by international law.'Israel said the flotilla was set to violate a 'lawful naval blockade' it has imposed on Gaza.The activists who set sail as part of the Global Sumud Flotilla include Mandla Mandela, the grandson of Nelson Mandela, as well as British citizens including a former RAF pilot.They were expected to be transferred to the immigration authority upon arrival in Ashdod, from where they would be transferred to Ketziot Prison in southern Israel, according to Suhad Bishara, the director at Adalah, a human rights organisation and legal centre in Israel. A Foreign Office spokesman said: 'We are very concerned about the situation with the Sumud flotilla. We are in touch with the families of a number of British nationals involved and we have been in contact with the Israeli authorities to make clear that we expect the situation to be resolved safely, in line with international law and with due respect for the rights of all those on board.'The aid carried by the flotilla should be turned over to humanitarian organisations on the ground to be delivered safely into Gaza.'