Activists released from Israeli custody after being detained on a flotilla trying to bring aid to Gaza were subjected to abuse, organizers said on Friday, with several hospitalized with injuries and at least 15 reporting sexual assaults, including rape.

Israel’s prison service denied the allegations, and Reuters was not able to verify them independently.

Germany said some of its nationals had been injured and that some accusations were “serious”, without giving further details. A legal source in Italy said prosecutors there were investigating possible crimes including kidnapping and sexual assault.

“The allegations raised are false and entirely without factual basis,” an Israeli prison service spokesperson said in a statement.

“All prisoners and detainees are held in accordance with the law, with full regard for their basic rights and under the supervision of professional and trained prison staff,” it said. “Medical care is provided according to professional medical judgment and in accordance with Ministry of Health guidelines.”

The Israeli military referred queries to the Foreign Ministry, which referred them to the prison service.

Israeli forces arrested 430 people on board 50 ships in international waters on Tuesday to halt a flotilla of volunteers trying to bring aid supplies to the Gaza Strip.

The allegations of abuse will add to pressure on Israeli authorities to explain the treatment of the detainees, after video of an Israeli cabinet minister in a prison mocking some of the activists sparked an international outcry. Italy said EU members were discussing imposing sanctions on the minister, Itamar Ben-Gvir.

“At least 15 cases of sexual assaults, including rape. Shot with rubber bullets at close range. Tens of people’s bones broken,” organizers of the Global Sumud Flotilla posted on the Telegram social media app.

“While the world’s eye is trained on the suffering of our participants, we cannot emphasize enough that this is a mere glimpse of the brutality Israel imposes daily on Palestinian hostages.”

‘Stripped, Thrown to the Ground, Kicked’

Luca Poggi, an Italian economist among those detained aboard the flotilla, told Reuters on his arrival in Rome: “We were stripped, thrown to the ground, kicked. Many of us were tasered, some were sexually assaulted, and some were denied access to a lawyer.”

Ilaria Mancosu, an Italian activist, said the flotilla members were removed from their boats to two so-called prison ships. Those put on one of the ships suffered more violence than the other. They were locked in a container and beaten by five soldiers, suffering fractures to the ribs and arms. Some had serious injuries to their eyes and ears caused by tasers.

She said they spent two days on the prison ships with no running water and used cardboard and plastic to keep warm at night since they had no blankets and were stripped of most of their clothes. Once on land they were made to kneel for several hours and kicked and shoved if they moved or spoke. They were then taken to a prison where they were moved from room to room periodically to keep them from sleeping, she said.

Rome prosecutors are investigating the possible crimes of kidnapping, torture and sexual assault and will hear testimony from activists who have returned to Italy over the coming days, the Italian legal source said.

A German Foreign Ministry spokesperson said consular officials who met German activists on their arrival in Istanbul reported that a number had injuries and were undergoing medical checks.

Humane treatment of German nationals was an “absolute priority,” the spokesperson said, and “we naturally expect a full explanation, as some of the allegations that have been made are serious.”

Sabrina Charik, who helped organize the return of 37 French citizens from the flotilla, told Reuters five French participants had been hospitalized in Turkey, some with broken ribs or fractured vertebrae. Some had made detailed accusations of sexual violence, including of rape, she said.

Activist Shows Bruises Across His Back and Forearms

In an Instagram post by an activist group verified by Reuters, French national Adrien Jouen showed bruises across his back and on his forearms.

Activists said some of the alleged abuse took place at sea after their interception by Israeli naval forces, and some following their arrest and imprisonment in Israel.

Spain’s Foreign Minister Jose Manuel Albares told reporters that 44 Spanish flotilla members were expected to arrive on Friday on flights from Istanbul to Madrid and Barcelona. Four of them had received medical treatment for injuries, he added.

Western governments on Thursday had expressed their anger after Ben-Gvir posted a video of himself mocking activists being pinned to the ground in a prison.

Italian Foreign Minister Antonio Tajani said on the sidelines of the NATO meeting in Sweden that he was in touch with all his EU counterparts “so that there may be a quick decision to impose sanctions” on Ben-Gvir.

EU foreign policy chief Kaja Kallas proposed last year imposing sanctions on Ben-Gvir and another Israeli minister, but the proposal did not garner the needed support of all the EU’s 27 member countries at the time.

(Reporting by Anna Uras, Rami Ayyub, Alvise Armellini, Layli Foroudi, Cristiano Corvino, Roberto Mignucci, Catherine Cartier, David Latona and Charlotte Van CampenhoutWriting by Charlie DevereuxEditing by Peter Graff, William Maclean)