- At least four Israelis have been killed and eight injured when two men with a pistol, knives and axes attacked a West Jerusalem synagogue, police say.
The attackers - Palestinians from East Jerusalem - were shot dead, police say.
Jerusalem has seen tensions between Israelis and Palestinians soar, with a string of deadly attacks and clashes over a disputed holy site.
Israeli Prime Minister Benjamin Netanyahu has vowed to respond "with a heavy hand to the brutal murder".
"This is a direct result of incitement led by Hamas and [Palestinian President Mahmoud Abbas, known as] Abu Mazen, incitement that the international community has been irresponsibly ignoring," he said in a statement.
Hamas and Mr Abbas's Fatah party - both rival Palestinian factions - agreed to form a unity government earlier this year, in a move denounced at the time by Israel.
Hamas and another Palestinian Islamist militant group, Islamic Jihad, praised the attack. Israel has designated both groups as terrorist organisations. There has been no comment so far from Mr Abbas.
The attacks happened at a religious seminary site on Harav Shimon Agassi Street - a largely orthodox area in the Har Nof neighbourhood.
Police say there was a shoot-out with the attackers when officers reached the scene.
Pictures posted online by an Israeli military spokesman show a bloodied meat cleaver - apparently used in the attack - inside the building.
An injured man still wearing his prayer shawl can also be seen lying on the ground.
"I tried to escape. The man with the knife approached me. There was a chair and table between us... my prayer shawl got caught. I left it there and escaped," one of the Israelis told Channel 2 television.
Police spokesman Micky Rosenfeld said the incident was being viewed "as a terrorist attack". He said the area had been sealed off and the injured - six worshippers and two policemen - were being treated in Jerusalem hospitals. Four are said to be in a serious condition.
Mr Rosenfeld told the BBC the attackers were killed at the entrance to the building. No other attackers were involved, he said.
Jerusalem on edge
Tensions in the city have risen in recent weeks, with two deadly attacks by Palestinian militants on pedestrians in the city and announcements by Israel of plans to build more settler homes in East Jerusalem.
A prominent rabbi and leading campaigner was shot and wounded last month by a Palestinian in Jerusalem at a key religious compound in the city.
The compound - known to Jews as the Temple Mount and to Muslims as al-Haram al-Sharif - is the holiest site in Judaism, while the al-Aqsa Mosque is the third holiest site in Islam.
Orthodox Jewish campaigners in Israel are challenging the long-standing ban on Jews praying at the compound.
Palestinians want East Jerusalem, occupied by Israel since 1967, as the capital of a future state.
Israel and the Palestinian Authority have blamed each other for the recent unrest in the city.
Jerusalem's holiest site
Known as the Temple Mount to Jews and al-Haram al-Sharif to Muslims, it comprises the al-Aqsa Mosque and the Dome of the Rock, and is next to the Western Wall
The Western Wall, from the time of the second Jewish Biblical temple, is the holiest site where Jews can pray; the Dome of the Rock, where according to Jewish tradition the Ark of the Covenant rested in the first temple, is the holiest site in Judaism
The al-Aqsa Mosque is the third holiest site in Islam; the Dome of the Rock is revered by Muslims because of its connections to the Prophet Muhammad
Christians also venerate the site because of its Biblical links to Jesus
A Muslim committee has managed the compound since the time of the Crusades, while Israel, which has occupied East Jerusalem since 1967, controls access
Israel maintains a ban on prayer by non-Muslims at the compound as a security measure
Rabbi Yehuda Glick campaigns for allowing Jews to pray at the site
Credit: The BBC
BY: The BBC
Category: Middle East