The families of Israeli victims of Palestinian attacks appealed Monday against the imminent release of long-serving Palestinian prisoners as part of US-brokered peace talks, media reported.
The Supreme Court has always rejected such appeals.
Israeli Prime Minister Benjamin Netanyahu had agreed to the phased release of 104 Palestinian prisoners in line with commitments to the US-backed talks, which resumed in July, and previous batches were freed in August and October.
The 26 prisoners expected to be released late on Monday were jailed before the signing of the 1993 Oslo accords, which formally launched the Middle East peace process, and have served 19 to 28 years for killing Israeli civilians or soldiers.
The release was expected to begin at 2200 GMT Monday, just days before US Secretary of State John Kerry is due back in the region for the latest round of talks.
Emotions run high on both sides over the issue of Palestinian prisoners, with Israelis viewing jailed militants as murderers and Palestinians hailing them as heroes imprisoned for fighting against the Israeli occupation.
"One of the things we knew when we captured these detainees is that they needed to stay in prison for the maximum period," Meir Indor, director of the Almagor, the Israeli group launching the appeal, told the Jerusalem Post.
"These men are time bombs. Wherever they go they kill, because that's the purpose of their lives."
Issa Qaraqae, the Palestinian minister of prisoner affairs, dismissed the Israeli complaints, saying: "Israel is a murderous state and these prisoners are freedom fighters."
Palestinian president Mahmud Abbas has called for the release of all Palestinian prisoners held by Israel and was to welcome those released Monday at an official ceremony in the West Bank city of Ramallah.
Israel holds more than 5,000 Palestinians in its prisons, most of them on security grounds. Around 150 are held under administrative detention, without charge or trial, and another 150 are minors.
To the fury of the Palestinians, the two previous prisoner releases were accompanied by announcements of new construction plans for Jewish settlements in the occupied West Bank, including annexed Arab east Jerusalem.
Monday's release is expected to be no different, despite US and EU appeals against such announcements.
Israeli media reports suggested Netanyahu was likely to unveil plans to build an additional 1,400 housing units, on top of those already announced, following strong pressure from ultra-nationalist members of his governing coalition.
Eighteen of the prisoners to be released Monday are from the occupied West Bank, with another three from Gaza and five from annexed east Jerusalem, according to Sivan Weizman, a spokesman for the Israeli prisons service.
Families of Israeli victims have accused Netanyahu of reneging on promises not to release east Jerusalem residents, who have ID cards that entitle them to social services.