JERUSALEM — Israel’s Supreme Court on Monday rejected appeals for the release of two Palestinian prisoners who have been on a hunger strike for 69 days to protest their incarceration without formal charges, sharpening concern for their lives and raising the specter of widespread unrest in the event of a death.

Barring a last-minute deal, Physicians for Human Rights-Israel, an advocacy group that has been monitoring the condition of the two men, said the court ruling was “the effective equivalent of handing down a death sentence.”

The judges said they had found no justification to intervene in the cases of Bilal Diab, 27, and Thaer Halahleh, 33, both residents of the West Bank accused of working with Islamic Jihad, an extremist organization. The court upheld the practice of imprisonment without charge — called administrative detention — if used sparingly. Yet the judges expressed unease over aspects of these particular cases and suggested that the authorities consider alternative approaches.

Citing classified evidence against Mr. Halahleh, the court said he had been engaged in transferring money for Islamic Jihad. But since Mr. Halahleh will have been in detention for almost two years when his current term ends in June, the court said, any further extension should be based on a more thorough investigation.

Mr. Diab, who previously spent years in prison on charges of military activity, according to court documents, was last detained in August 2011. Citing secret evidence that he played an organizational role in Islamic Jihad, also mainly related to money, the court suggested that the military authorities should consider administrative terms shorter than six months in Mr. Diab’s case, to allow for better judicial oversight.

In addition, one of the judges suggested that given the deteriorating health of the men, the authorities could consider the option of releasing them on parole.

Islamic Jihad is notorious for the suicide bombings it carried out last decade in Israeli cities, and more recently for firing rockets from Gaza into southern Israel. Spokesmen for the group have warned of dire consequences if a hunger striker dies.

Israel argues that administrative detention is necessary to ensure security. It currently holds more than 300 Palestinian administrative detainees, whose terms of up to six months can be renewed repeatedly.

Adding to the tensions, at least 1,500 convicted Palestinian security prisoners from various organizations have joined the hunger strike since mid-April, demanding better prison conditions.

The protest began with Khader Adnan, a detainee from Islamic Jihad who fasted for 66 days until he reached a deal in February for his release in April. Another detainee, Hana Shalabi, also believed to be a member of Islamic Jihad, fasted for more than 40 days before being sent into temporary exile in Gaza. Neither case caused any fundamental change in Israeli policy.

In a separate ruling Monday, the Supreme Court rejected an appeal by the state to reopen a highly contentious case involving five apartment buildings in Ulpana, a development linked to the Jewish settlement of Bet El in the West Bank.

The state had pledged to demolish the buildings, home to about 30 Israeli families, by May 1, in accordance with an earlier court ruling because they were built, albeit with government subsidies, on privately-owned Palestinian land. But the government, faced with a political challenge, recently asked the court to reconsider its ruling.

The judges said on Monday that the state had presented no legal precedent and no new facts to warrant such an extraordinary step. The court gave the state until July 1 to demolish the buildings.

Yesh Din, an Israeli human rights organization representing the Palestinian landowners, welcomed the decision, saying it upheld the rule of law.