Two Palestinian men armed with a meat cleaver and a gun killed fourJews worshiping at morning prayers (Update: and one police officer) in a West Jerusalem synagogue early Tuesday, reports Reuters. Israel’s ambulance service said that several other people were seriously wounded.

The attack was the deadliest in Jerusalem in six years, and comes during a surge in Arab violence in recent weeks. Three of the dead were U.S. citizens, and one, Rabbi Moshe Twersky, was the son of a well-known Harvard professor.

Prime Minister Benjamin Netanyahu promised that Israel will “respond decisively.”  He called the attack a “cruel murder of Jews who came to pray and were killed by despicable murderers,” reports the Jerusalem Post

Netanyahu added that the synagogue attack was “a direct result of incitement” by Hamas and Palestinian Authority president Mahmoud Abbas, “incitement that the international community has been irresponsibly ignoring.”

U.S. Secretary of State John Kerry condemned the attack. “Innocent people who had come to worship died in the sanctuary of a synagogue. They were hatcheted, hacked and murdered in that holy place in an act of pure terror and senseless brutality and murder,” Kerry said, as reported by the New York Post.

Abbas also condemned the attack–somewhat. While condemning the killing, he criticized Israeli actions in same breath. In a statement, Abbas’s office said he “condemns the killing of the worshippers in a synagogue in west Jerusalem,” but he also called for an end to the “invasion” of the al-Aqsa mosque and a halt to “incitement” by Israeli government ministers.

One of the worshipers at Kehillat Bnei Torah synagogue in the ultra-Orthodox Jerusalem neighborhood Har Nof, Yosef Pasternak, said about 25 people were praying when shooting broke out.

Other witnesses described the scene as reminiscent of the slaughter of Jews in Europe during the Holocaust, with Jews wrapped in talitot (prayer shawls) and tefilin (phylacteries) dying in pools of their own blood on the floor of the synagogue.

Photos from the scene were gruesome, showing a man in a Jewish prayer shawl lying dead, a bloodied butcher’s cleaver on the floor, and several overturned prayer tables and prayer books covered in blood.

The two assailants, both from predominantly Arab East Jerusalem, were shot dead by police.

Besides Abbas’s half-condemnation, other Palestinian organizations celebrated the attack. The terror group Popular Front for the Liberation of Palestine (PFLP), claimed credit for carrying out the operation.

“We declare full responsibility of the PFLP for the execution of this heroic operation conducted by our heroes this morning in Jerusalem,” said Hani Thawbta, a PFLP leader in Gaza.

The attackers were lauded as “martyrs” on Palestinian radio. Loudspeakers at Gaza mosques congratulated the perpetrators, and people in the streets celebrated by handing out candy.

The Islamist group Hamas praised the mission. “Hamas calls for the continuation of revenge operations and stresses that the Israeli occupation bears responsibility for tension in Jerusalem,” Hamas spokesman Sami Abu Zuhri said.

Violence in and around Jerusalem has surged in the past month, where five Israelis and a foreign visitor have been deliberately run over and killed by Arab drivers or stabbed to death by Palestinians. 

This article has been updated to reflect the latest number of reported dead.

Image: Israel MFA/Twitter