A Palestinian man on hunger strike for nearly 80 days since his arrest by Israel in late July is "on the verge of death", Israeli rights group B'Tselem said Monday.
Maher al-Akhras, 49, was arrested near Nablus and placed in administrative detention, a policy that Israel uses to hold suspected terrorists without charge.
The married father of six launched his strike to protest the policy.
He has been arrested several times previously by Israel, which accuses him of having ties to the Islamic Jihad terrorist group.
At the Ofer Prison in the West Bank, 32 Palestinian prisoners have begun a hunger strike in solidarity with al-Akhras.
The 32 security prisoners were “punished immediately,” Israel Prison Service said.
“They were transferred into isolation and placed in empty cells without any equipment,” the official prison body added.
On Monday, some 40 people held a rally in the West Bank city of Ramallah to support him.
"Our people will not let Maher al-Akhras down," said Khader Adnan, one of those taking part in the rally, and who has himself carried out a several hunger strikes in Israeli captivity.
Adnan called on the international community and Palestinian leaders to pressure Israel over the case.
"Do more over the coming hours," he said. "We are in the critical stage."
Palestinian Prime Minister Mohammad Shtayyeh demanded Akhras' "immediate release," according to a statement on the official Wafa news agency.
Akhras was transferred in early September to Kaplan Medical Center in Rehovot in central Israel.
His lawyers have appealed on multiple occasions to the Supreme Court for his release, including at a hearing on Monday.
The justices deferred a ruling on Monday's request, saying the case remained under review, according to a summary of the hearing seen by AFP.
AFP made repeated efforts to contact his legal team on Monday.
Israel's administrative detention system, inherited from the British mandate, allows the internment of prisoners for renewable periods of up to six months each, without bringing charges.
Israel says the procedure allows authorities to hold suspects and prevent attacks while continuing to gather evidence, but critics and rights groups say the system is abused.
Around 355 Palestinians were being held under administrative detention orders as of August, including two minors, according to B'Tselem.