A Palestinian prisoner who was wounded in rioting at an Israeli desert prison died early Tuesday, prompting Palestinian threats of revenge and accusations that the man was abused by Israeli authorities.

The death, along with an Israeli raid in the West Bank that killed two Palestinian militants, raised tensions at a time when the Israeli and Palestinian leaders are trying to move forward with preparations for a U.S.-sponsored peace conference later this year.

The Israeli Prisons Service said the wounded man died at an Israeli hospital, hours after he was hit by a "non-lethal weapon" fired by guards during Monday's riot at the Ketziot prison. The prison guards' lives were in danger when they opened fire, it said.

The prisons service did not elaborate on the cause of death and did not identify the inmate, saying only that he was 30 and had been serving a two-year sentence for harboring a wanted militant.

Ashraf Ajrami, minister of prisoner affairs in the Palestinian government, identified him as Mohammed al-Ashkar, a member of the Islamic Jihad militant group. He said the relatively short sentence suggested his offense must have been minor.

The violent Islamic group Hamas, whose members took part in the 2006 abduction of Israeli soldier Gilad Shalit, warned that he could suffer in retribution for the killing of al-Ashkar.

The group's military wing said it would "not stand idle before the attacks on the prisoners and has painful options for the enemy regarding the case of Shalit and other issues." It did not elaborate.

Mushir al-Masri, a Hamas lawmaker, also vowed revenge. "The resistance factions will not stand idly by and all options are open to us to face this dangerous policy," he said.

Hamas and Islamic Jihad have killed hundreds of Israelis in suicide bombings, shootings and rocket attacks.

Violence erupted before dawn Monday at Ketziot — where about 2,200 Palestinians are imprisoned for security offenses — when guards began searching prisoners' bunks for contraband. Ketziot is set up like a military camp, and security prisoners are quartered in tents.

Prisoners torched several tents and attacked guards, injuring 15 of them, the prisons service said. When anti-riot forces moved in, 15 prisoners were injured, four of whom were taken to the hospital, including the man who later died. The other injured prisoners were not in danger, the prisons service said.

Ajrami said the overnight sweep that sparked the rioting violated an agreement between the prisons service and inmates barring nighttime searches.

But Ian Domnitz, a prison service spokesman, said there was no such agreement with the prisoners.

Israel is holding 11,000 Palestinian prisoners for security offenses ranging from membership in militant organizations to planning and carrying out attacks.

Their release is a central Palestinian demand.

In the West Bank town of Bethlehem, about 500 people rallied downtown Tuesday, protesting al-Ashkar's death and calling for the release of all Palestinians held by Israel. About the same number took to the streets in Nablus, among them mothers carrying pictures of their imprisoned sons. At least one protester fired into the air.

Also in the West Bank, about 200 people took part in a similar march in Ramallah, chanting, "We want the prisoners, not negotiations" with Israel.

In Gaza City, about 300 demonstrators called for the release of prisoners. Nidal Saraffati, father of a 24-year-old jailed in Israel, said inmates are subjected to regular abuse and their plight should unite all Palestinians.

"This is an attack on the family and the prisoners as well," he said. "We ask all the brothers to leave internal fighting behind. We have one common enemy."

In a separate development, Israeli troops killed two Palestinian militants in a fierce gunbattle in the northern West Bank town of Jenin, witnesses and army reports said. Islamic Jihad said the two dead were its members, and one of them was a top leader in the West Bank.

The army said one soldier was slightly wounded in the fight, which began shortly after soldiers surrounded a house used by wanted men. Six people were arrested, it added.