The Israel Prison Service informed Sarhan's family on Sunday of his death, but did not provide details about the circumstances surrounding it.
Sarhan, 48, was from the Wadi Nisnas neighbourhood of Haifa and had been imprisoned since January 2002. He was serving a life sentence plus 10 years.
The Palestinian Commission of Detainees' Affairs and the Palestinian Prisoners Society said Sarhan underwent more than two months of interrogation following his arrest and spent years under harsh detention conditions.
According to the two organizations, he was repeatedly subjected to torture and punitive measures, including extended periods in solitary confinement. They said he spent four consecutive years in isolation after Israeli authorities placed him under what they described as a "secret file", with the isolation order repeatedly renewed.
The groups said years of imprisonment and detention conditions had contributed to serious health complications. Sarhan suffered from chronic illnesses affecting his heart, arteries, and veins, in addition to high blood pressure and other ailments, they said.
In 2022, the Commission of Detainees' Affairs reported that his condition had deteriorated to the point that he required a wheelchair. The organizations accused Israeli prison authorities of failing to provide adequate medical care and described Sarhan as one of the prisoners affected by systematic medical neglect.
His death comes amid mounting concerns raised by Palestinian prisoner groups over conditions inside Israeli prisons and a rise in the number of detainee deaths since the start of Israel's genocidal war on Gaza in October 2023.
According to the Commission of Detainees' Affairs and the Palestinian Prisoners Society, Sarhan's death raises the number of Palestinian prisoners whose identities have been announced since October 2023 to 90. The groups said the total number of Palestinians who have died in Israeli custody since 1967 has reached 327.
They said the latest figure represents the highest documented death toll over a comparable period in the history of the Palestinian prisoner movement, attributing the increase to worsening detention conditions, including torture, prolonged isolation, food deprivation, and inadequate medical treatment.
The two organizations said conditions in Israeli prisons have deteriorated sharply since October 2023, with prisoners facing tighter restrictions and reduced family contact. They also said representatives of the International Committee of the Red Cross have been unable to carry out regular visits to Israeli prisons since the beginning of the war.
Following Sarhan's death, the groups called on international human rights bodies to investigate conditions inside Israeli prisons and pursue accountability for alleged violations.
According to figures released by Palestinian prisoner organizations, more than 9,400 Palestinians are currently being held in Israeli prisons, including 3,324 administrative detainees held without charge or trial and 1,316 prisoners classified by Israeli authorities as "unlawful combatants".
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