JERUSALEM (AP) ― Israel vowed harsh retaliation Tuesday for a Palestinian attack that killed five people and left blood-smeared prayer books and shawls on the floor of a synagogue in Jerusalem ― an assault that sharply escalated already-high tensions after weeks of religious violence.

The attack during morning prayers in the west Jerusalem neighborhood of Har Nof was carried out by two Palestinian cousins wielding meat cleavers, knives and a handgun. They were shot to death by police after the deadliest assault in the holy city since 2008.

Four of the dead were rabbis and one was a police officer who died of his wounds hours after the attack. Three of the rabbis were born in the United States and the fourth was born in England, although all held dual Israeli citizenship. Five others were wounded.

Palestinian President Mahmoud Abbas condemned the attack, the first time he has done so in the wave of deadly violence against Israelis. But he also called for an end to Israeli “provocations” surrounding Jerusalem’s shrines that are sacred to both Muslims and Jews.

President Barack Obama called the attack “horrific” and without justification, urging cooperation from both sides to ease tensions and adding that too many Israelis and Palestinians have died in recent months.

Tuesday’s attack, however, appeared to mark a turning point, with the gruesome scene in a house of worship shocking a nation long accustomed to violence.

The government released a photo of a meat cleaver it said came from the crime scene. Government video showed blood-soaked prayer books and prayer shawls in the synagogue. A pair of glasses lay under a table, and thick streaks of blood smeared the floor.

“I saw people lying on the floor, blood everywhere,” said Yosef Posternak, who was at the synagogue in the quiet neighborhood that has a large community of English-speaking immigrants.

“People were trying to fight with (the attackers) but they didn’t have much of a chance,” Posternak told Israel Radio.

In one of Israel’s first acts of retaliation, Prime Minister Benjamin Netanyahu ordered the demolitions of the homes of the attackers. But halting further violence could prove to be a tough challenge as police confront a new threat: Lightly armed assailants from annexed east Jerusalem who hold residency rights that allow them to move freely throughout the country.

Netanyahu condemned the deaths of the “innocent and pure Jews.” In a nationally televised address, he accused Abbas of inciting the recent violence and said the Palestinian leader’s condemnation of the attack was insufficient.

Hamas, the militant Palestinian group that runs the Gaza Strip, praised the attack. In Gaza, dozens celebrated in the streets, with some offering trays full of candy.

The U.S.-born victims were identified as Moshe Twersky, 59, Aryeh Kupinsky, 43, and Kalman Levine, 55. The Israeli Foreign Ministry said the British man was Avraham Goldberg, 68, who immigrated to Israel in 1993.

It described the four as “rabbis,” an honorific title in the ultra-Orthodox world given to men who are considered pious and learned. Twersky, a native of Boston, was the head of the Toras Moshe Yeshiva, a seminary for English-speaking students. He was the son of Rabbi Isador Twersky, founder of Harvard University’s Center for Jewish Studies, and a grandson Rabbi Joseph B. Soloveitchik, a luminary in the world of modern Orthodox Jewry.

Thousands of people attended a joint funeral for Kupinsky, Levine and Goldberg before sundown ― held outside the synagogue where they were killed.

In recent weeks, Jerusalem has seen its worst sustained bout of violence since a Palestinian uprising a decade ago. Palestinian assailants have carried out a pair of deadly attacks by ramming their cars into crowded train stations, while a gunman shot and seriously wounded a Jewish activist who has campaigned for greater access to the holy site.