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.