By Maayan Lubell
JERUSALEM (Reuters) - Two Palestinians armed with a meat cleaver and a gun killed four worshippers in a Jerusalem synagogue on Tuesday 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 U.S.-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 inciting violence in Jerusalem.
Abbas condemned the attack, which comes after weeks of unrest fueled 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 neighborhood 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.
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.
The Popular Front for the Liberation of Palestine, said it carried out the attack, which it called a "heroic operation".
Police identified one of the dead as Rabbi Moshe 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.
Twersky and two other victims, Aryeh Kopinsky and Calman Levine, were U.S. and Israeli citizens. The British-Israeli killed in the attack was named as Avraham Shmuel Goldberg.
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."
U.S. 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.
"MARTYRS"
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 toward 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, fueled 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 Tuesday'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 war between Israel and Hamas in Gaza 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.
(Additional reporting by Nidal al-Mughrabi and Noah Browning; Editing by Jeffrey Heller, Luke Baker and Giles Elgood)