Jerusalem (CNN) -- Entering the 80th day of a hunger strike Wednesday, former Palestinian national football player Mahmoud Sarsak said he will continue until he is released from the Israeli prison where he has been held without charge since July 2009.
Sarsak is protesting Israel's controversial policy of "illegal combatant" -- also known as administrative detention -- which allows Israeli authorities to detain Palestinians indefinitely.
Also Wednesday, two human rights organizations expressed concern about Sarsak and two other hunger strikers: Akram Rikhawi, whose protest was entering its 56th day, and Samer Al-Barq, who's been held since July 2010.
A month ago, most of the 1,650 Palestinian prisoners on a hunger strike against administrative detention ended their protest after an Egyptian-mediated agreement between Israeli and Palestinian authorities to improve prison conditions. However, Sarsak and a handful of other prisoners continued to starve themselves.
Israeli government spokesman Mark Regev told CNN that Sarsak's case "has been brought before numerous judges who have seen the evidence and have ruled in favor of his continued detention. He is part of Islamic jihad, one of the most extreme Iranian-supported terrorist organizations, that has a track record of brutal murder against innocent civilians."
A native of the southern Gaza Strip city of Rafah, Sarsak, 25, was on his way to join the Balata football team in the West Bank when he was arrested three years ago despite having the proper Israeli permits to travel, his family told CNN.
"The Israeli occupation is unjust in arresting my brother without any reason," Imad, Sarsak's 36-year-old brother, told CNN.
"He has been in an Israeli prison for more than three years without any charge. On what basis does Israel arrest him? He was not carrying any explosives, only his football outfit and his football shoes. Israel is violating international law, my brother does not belong to any militant organization," Imad Sarsak said.
Human rights lawyers contest Israel's detention of Sarsak and say it is politically motivated.
"The use of the 'illegal combatant law,' like in the case of Mahmoud Sarsak, is a political reason and not a security reason as Israel is claiming," said Sahar Francis, the director of Addameer, a group that advocates human rights and provides prisoner support.
Francis went further, accusing Israel of detaining him to damage his career.
Sivan Weizman, a spokeswoman for the Israeli prison service, told CNN that "Sarsak has not been on a hunger strike for all the 80 days; he eats and restarts his hunger strike. He is in an Israeli military medical center and getting medical care."
But human rights activists are worried about his health.
In a joint statement, Physicians for Human Rights-Israel and the Palestinian Council of Human Rights Organizations said that Sarsak's protest has caused "an imminent threat to his life." They say he has lost muscle tissue and 33% of his body weight, and suffers from frequent fainting and lapses in memory. They also said pulse disruptions are endangering his life.
Anat Litvin, the director of prisoners and detainees for Physicians for Human Rights-Israel, told CNN that "Sarsak is the longest Palestinian on hunger strike, and we are afraid that the medical center of the Israeli prison service is not the right place for him to be, because they are not able to give him the proper treatment, especially if something happens in his condition while on hunger strike. The fear is that there will be rapid deterioration; they cannot perform medical tests such as blood tests and ultrasound or an X-ray on the spot."
Rikhawi, the statement said, has lost muscle tissue and a drastic amount of weight, and needs immediate hospitalization. He has been in a prison medical center "since his arrest in 2004, as he suffers from many different chronic conditions." Doctors are force-feeding him, the statement said.
The human rights groups said that Al-Barq, 38, began his hunger strike in April, suspended it on May 14 and restarted it on May 21.
The statement called for the strikers to be moved to civilian hospitals with access to independent doctors and family members, and urged the United Nations, United States and Europe to pressure Israel to end administrative detention.
An Amnesty International report released Wednesday calls on the Israeli government to release all prisoners held under administrative detention or to give them fair trials.
Titled "Starved Justice," the report says that the nonviolent protests, which brought several detainees close to death, drew global attention to the fact that Palestinian prisoners held by Israel continue to be starved of justice.
The report also alleges torture and ill treatment during interrogations of Palestinian prisoners, especially those held under administrative detention.