Rabbis killed in meat cleaver and gun attack were US and UK citizens

The victims of a deadly Palestinian attack on a Jerusalem synagogue included three Americans and a British citizen, Israeli police say.

There was no immediate word on their identities but Israel's leading ultra-Orthodox website said all four, who had dual Israeli nationality, were rabbis.

"Regarding citizenship, there were three Americans and the fourth was British," police spokeswoman Luba Samri said.

They were killed when two Palestinians entered a yeshiva Jewish seminary in a district on the western flank of the city and attacked them with meat cleavers and a gun, resulting in what eyewitnesses called scenes of carnage.

The bloodshed took place as months of unrest gripped Jerusalem's annexed Arab eastern sector, resulting in a string of deadly attacks by lone Palestinians and further inflamed by the death of a Palestinian bus driver in controversial circumstances.

But none was as serious as Tuesday's killings at the synagogue in an ultra-Orthodox neighbourhood on the city's western outskirts as worshippers gathered for morning prayers.

Four people were killed and eight wounded, including two policemen, medics said. One person was in a critical condition and three sustained serious injuries, with eyewitnesses saying several had had limbs hacked off.

The attack began on Tuesday morning local time when the assailants burst in, waving meat cleavers and a gun at the synagogue in a Jewish seminary in Har Nof.

Three policemen - two traffic officers and a forensics expert - arrived and exchanged gunfire with the attackers, killing them, police spokeswoman Luba Samri said.

Two policemen were wounded, one critically.

The assailants were identified by family members as Uday and Ghassan Abu Jamal, cousins from the east Jerusalem neighbourhood of Jabal Mukaber. Both were in their 20s.

Israel vowed a harsh response, with Prime Minister Benjamin Netanyahu calling the bloodshed a "direct result" of incitement by Palestinian president Mahmud Abbas and Hamas, vowing to respond with "a heavy hand".

Abbas condemned the killings, but Hamas welcomed the attack, describing it as a fitting "response" to Israeli actions in annexed east Jerusalem.

Analysts warned of escalation in a situation already fraught with tension.

"This event has the potential of being a game changer," said Kobi Michael, senior researcher at the Institute for National Security Studies, adding it created a sense that things were "out of control".