Emergency services volunteers carry the body of a Palestinian assailant who was shot dead while attacking the synagogue.
The attack comes among frustrating tensions in Jerusalem, which has seen a spate of attacks by Palestinians against Israelis. At least six people have been killed in Jerusalem, the West Bank and Tel Aviv in recent weeks, prior to Tuesday’s casualties.
Four Israelis have been
killed and eight injured as two men armed with a pistol and meat
cleavers attacked a West Jerusalem synagogue, police say.
The attackers - Palestinians from East Jerusalem - were shot dead.There have recently been several deadly attacks and clashes in Jerusalem, which has also seen heightened tension over a disputed holy site.
Israel has vowed to respond "with a heavy hand" to the attack - the deadliest in Jerusalem in six
Prime Minister Benjamin Netanyahu blamed "incitement" by Hamas and Palestinian President Mahmoud Abbas, and said the international community had ignored their actions.
Hamas and Mr Abbas's Fatah party - rival Palestinian factions - agreed to form a unity government earlier this year, a move denounced at the time by Israel.
Mr Abbas's office issued a statement saying: "The presidency condemns the attack on Jewish worshippers in their place of prayer and condemns the killing of civilians no matter who is doing it."
The Abu Ali Mustafa Brigades, the military wing of the Popular Front for the Liberation of Palestine, says it carried out the synagogue attack.
Militants from the far-left-wing Palestinian nationalist group have been behind many previous attacks on Israelis.
Hamas and another militant group, Islamic Jihad, praised the attack. Israel has designated both groups as terrorist organisations.
In the last few weeks tensions have risen sharply - largely as the result of the revival of an ancient dispute over rights of worship at a site within the walls of the Old City.
Muslims call the site al-Haram al-Sharif and believe it is the place where the Prophet Muhammad ascended into heaven - to Jews it is Temple Mount and marks the place where the sacred temples of their faith stood in ancient times.
By a long-standing tradition, Muslims alone have the right to pray at the site although people of other faiths may visit.The issue is of such sensitivity that even when Israel captured the Old City of Jerusalem during the war of 1967 it handed control of the compound back to an Islamic religious authority which continues to administer it to this day.
In recent times some religious Jews have begun to argue for a change in the status quo which would also allow them to pray there - any hint of such change is viewed with deep anger in the Islamic world.
in the Gaza Strip, Palestinians distributed sweets in celebrations, some holding aloft an image of the attackers
The attack happened at a religious seminary site on Harav Shimon Agassi Street - home to a largely Orthodox Jewish community in the Har Nof neighbourhood. Among those killed was Rabbi Moshe Twersky, head of the seminary.
tension has been rising in jerusalem recently.
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, bodies lying between desks and chairs on a blood-stained floor, their faces covered with their prayer shawls.
"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.
details on BBC News