Adnan “refused to undergo medical tests and receive medical treatment” and “was found unconscious in his cell” in the early morning on Tuesday, the Israeli prison service said.
Adnan began his hunger strike shortly after being arrested on February 5.
He had gone on hunger strike several times after previous arrests, including a 55-day strike in 2015 to protest his arrest under so-called administrative detention, in which suspects are held indefinitely by Israel without charge or trial.
Israel is currently holding more than 1,000 Palestinian detainees without charge or trial, the highest number since 2003, according to the Israeli human rights group HaMoked.
“Khader Adnan has been executed in cold blood,” the WAED Prisoners Association in Gaza told the Reuters news agency upon hearing of Adnan’s death.
Palestinian news agency WAFA reported that Adnan, 44, from the town of Arraba near Jenin city in the occupied West Bank, had refused to eat for 87 days to protest against his detention without charge, according to the Palestinian Prisoner’s Society.
“This is a very dangerous thing that has happened,” said Mustafa Barghouti, the former Palestinian information minister and general secretary of the Palestinian National Initiative political party.
The Israeli government and National Security Minister Itamar Ben-Gvir “are personally responsible for this act of assassination”, Barghouti told Al Jazeera.
“I call it an act of assassination because the Israeli government knew very well, and its military courts, that a person who is on hunger strike for 87 days, who had not received any kind of medical care, could die at any moment. And that’s exactly what has happened,” Barghouti added.
“Mr Khader Adnan was arrested without charge. It’s not the first time. He has been arrested under what they call administrative detention, which means that Israel can arrest anybody without even saying why. Without any charges. Without any proof. Without a trial,” he continued, stating, “This is a country that is practising Fascism. Israel is a country that is practising unacceptable violations of human rights.”
A father of nine, Adnan had been arrested 12 times during his life and had undertaken hunger strike action during several stints in Israeli prisons, WAFA reported.
Last week, Adnan’s wife Randa Mousa told Agence France-Presse (AFP) news agency that her husband was being held in a clinic at Ramla prison in central Israel.
“(He is) refusing any support, refusing medical examinations, he is in a cell with very difficult detention conditions,” she said.
“They (Israel) have refused to transfer him to a civilian hospital, they refused to allow his lawyer a visit,” she added.
A medic from the group Physicians for Human Rights Israel who had visited Adnan in prison warned that he “faces imminent death”, while calling for him to be “urgently transferred to a hospital”, AFP reported.
The group announced Adnan “struggles to move and maintain a basic conversation, appearing pale, weak, exhausted and dangerously emaciated”, according to a statement released Monday by the group.
Adnan’s death has been called an “act of assassination”, Al Jazeera’s Ibrahim said, adding that Palestinians considered Adnan a political activist who had led the refusal of food as a means of protesting against imprisonment without charge by Israeli forces.
“Let’s not forget in 2012 he was the first to lead an individual hunger strike protesting his detention without charges, which was seen as a pioneer act leading the way for so many other prisoners to start hunger striking as a way to protest their detention,” Ibrahim stated.
