Two Palestinians armed with a meat cleaver and a gun killed four worshippers in a Jerusalem synagogue yesterday before being shot dead by police, the deadliest such incident in six years in the holy city amid a surge in religious conflict.

Three of the victims held dual US-Israeli citizenship and the fourth man was a British-Israeli national, police said.

Israeli Prime Minister Benjamin Netanyahu pledged to respond with a “heavy hand”, and again accused Western-backed Palestinian President Mahmoud Abbas of incitingviolence in Jerusalem.

Abbas condemned the attack, which comes after weeks of unrest fuelled in part by a dispute over Jerusalem’s holiest shrine.

A worshipper at the service in the Kehillat Bnei Torah synagogue in an ultra-Orthodox neighbourhood of West Jerusalem said about 25 people were praying when shooting broke out.

“I looked up and saw someone shooting people at point-blank range. Then someone came in with what looked like a butcher’s knife and he went wild,” the witness, Yosef Posternak, told Israel Radio.

We are viewing this as a terrorist attack

Photos distributed by Israeli authorities showed a man in a prayer shawl lying dead, a bloodied butcher’s cleaver on the floor and prayer books covered in blood.

“We are viewing this as a terrorist attack,” said police spokesman Micky Rosenfeld, who confirmed the four dead and that the two assailants, both from predominantly Arab East Jerusalem, had been shot dead by police.

Israel’s ambulance service said at least eight people were seriously wounded.

Israeli police and the US State Department identified one of the dead as Rabbi Mosheh Twersky, who taught at a Jerusalem seminary. Twersky was from a Hassidic rabbinical dynasty and a grandson of Joseph Soloveitchik, a renowned Boston rabbi who died in 1993.

Israeli emergency personnel carrying a covered body from the scene of an attack at a Jerusalem synagogue, yesterday. Photo: Ammar Awad/Reuters

Twersky and two other victims, Aryeh Kupinsky and Cary William Levine, were US citizens, according to the State Department and the Israeli police, which said they were also Israeli nationals. The British-Israeli killed in the attack was named by the police as Avraham Shmuel Goldberg.

The Popular Front for the Liberation of Palestine, said it carried out the attack, which it called a “heroic operation”.

In a statement, Abbas said: “The presidency condemns the attack on Jewish worshippers in one of their places of prayer in West Jerusalem and condemns the killing of civilians no matter who is doing it.”

US Secretary of State John Kerry described the attack as an act of “pure terror”.

Israeli Internal Security Minister Yitzhak Aharonovitch said he was seeking a partial easing of gun controls so that military officers and security guards could carry weapons while off-duty.

Palestinian radio described the attackers as “martyrs” and the Islamist group Hamas praised the attack. Loudspeakers at mosques in Gaza called out congratulations and youngsters handed out candy in the streets.

Palestinian media named the attackers as Ghassan and Udai Abu Jamal, cousins from the Jerusalem district of Jabal Mukaber, where clashes broke out as Israeli security forces moved in to make arrests.

“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.

The synagogue attack came a day after a Palestinian bus driver was found hanged in his vehicle in Jerusalem. Israel said he committed suicide, but his family said he was attacked.

Netanyahu said the synagogue attack was a result of incitement by Hamas and Abbas.

“We will respond with a heavy hand to the brutal murder of Jews who came to pray and were killed by lowly murderers,” he said.

At a meeting of Parliament’s Foreign Affairs and Defence committee, Yoram Cohen, head of the internal Shin Bet security service, appeared to take a softer line towards Abbas, saying he was not espousing terror, according to a political source.

But Cohen added: “There are those in the Palestinian public who might interpret his comments as legitimation for terror attacks”.

Violence in Jerusalem, areas of Israel and the Israeli-occupied Palestinian territories has surged in the past month, fuelled in part by a dispute over Jerusalem’s holiest shrine, and Abbas has said Muslims have a right to defend their sacred places if attacked.

Five Israelis and a foreign visitor were killed in the Palestinian attacks that preceded yesterday’s incident. About a dozen Palestinians have also been killed, including those accused of carrying out the attacks prior to the synagogue assault.

Residents trace the violence in Jerusalem to July, when a Palestinian teenager was burned to death by Jewish assailants, an alleged revenge attack for the abduction and killing of three Jewish teens by Palestinian militants in the occupied West Bank.

The summer Gaza war between Israel and Hamas and a row over access to a Jerusalem compound that is sacred to Muslims and Jews alike have also triggered violence.

The synagogue attack was the worst in the city since 2008, when a Palestinian gunman killed eight people in a religious school.