The Popular Front for the Liberation of Palestine (PFLP) has claimed responsibility for an attack that left four people dead at a synagogue in Jerusalem on Tuesday, Al-Arabiya news reported.
"The Abu Ali Mustafa Brigades, the armed wing of the PFLP, announce that both attackers were PFLP members," the group said in a statement.
The PFLP is revolutionary leftist organisation founded in 1967. It was known for its armed attacks on Israeli targets and aircraft hijackings. Its armed brigade, Abu Ali Mustafa, declared responsibility for many attacks during the Al-Aqsa Intifada in 2000.
Two Palestinians armed with a gun and axes burst into a Jerusalem synagogue on Tuesday morning and killed four Israelis before being shot dead, in the deadliest attack in the city in years.
The attack came as months of unrest gripped the city's annexed Arab eastern sector which has resulted in a string of deadly attacks by lone Palestinians.
But none was as serious as Tuesday's assault on the synagogue in an ultra-Orthodox neighbourhood on the city's western outskirts as worshippers gathered for the morning prayers.
Six other people were wounded, among them two policemen, before the two attackers were shot dead, police spokeswoman Luba Samri said, identifying them as Palestinians from east Jerusalem.
Palestinian Islamist group Hamas, which dominates Gaza, welcomed the deadly attack, saying it was a response to the death earlier this week of a Palestinian bus driver from east Jerusalem who was found hanged inside his vehicle.
Police said there was no evidence of foul play, blaming his death on suicide, with their findings backed up by a post-mortem.
But colleagues and family said there were signs of violence on his body, claiming he was murdered.
And the Palestinian pathologist who attended the post-mortem also ruled out suicide, suggesting he may have been drugged then strangled, the family's lawyer said.
Thousands attended his funeral late on Monday, some of them calling for revenge.
Arab east Jerusalem has been a tinderbox since early July when Jewish extremists killed a 16-year-old Palestinian in revenge for the murder of three Jewish teenagers, sparking a wave of clashes and rioting which has shown no sign of letting up.
The attack in Jerusalem began shortly before 7 am (0500 GMT) as worshippers were attending morning prayers at a synagogue in the ultra-Orthodox Har Nof neighbourhood.
"There are four dead and six injured, among them two policemen," the police spokeswoman said.
"Two terrorists, apparently from east Jerusalem, entered a yeshiva (Jewish seminary) in Har Nof and attacked worshippers with axes and a pistol," Samri said.
"Two policemen, who arrived quickly at the scene, engaged in a gunbattle with the terrorists who were shot dead."
Samri said the attackers were cousins from the east Jerusalem neighbourhood of Jabal Mukaber.
A witness, identified only as Zohar, said there was panic at the scene and a lot of blood.
"I heard shooting and one of the worshippers came out covered in blood and shouted 'There's a massacre'," he told the radio, saying there was sounds of shooting everywhere.
The attack 'result' of Abbas, Hamas incitement: Netanyahu
Israeli Prime Minister Benjamin Netanyahu said the attack was the result of "incitement" by Palestinian leader Mahmud Abbas as well as Hamas.
"This is the direct result of incitement by Hamas and Abu Mazen (Abbas), incitement that the international community ignores in an irresponsible manner," the premier said in a statement.
It said he would meet security chiefs during the afternoon.
Netanyahu has repeatedly accused Abbas of encouraging deadly attacks after the Palestinian leader called for people to take action following tensions at Jerusalem's flashpoint Al-Aqsa mosque compound, a site holy to both Muslims and Jews.
Months of tensions at the shrine appeared to have abated late last week following talks in Amman between Netanyahu, US Secretary of State John Kerry and Jordan's King Abdullah II.
Kerry condemned Tuesday's attack on the synagogue as an "act of pure terror and senseless brutality," and called on the Palestinian leadership to denounce it.
In Gaza, Hamas and its smaller rival Islamic Jihad said it was Israel that had sparked the attack as result of the bus driver's death and the tensions at the mosque compound.
"The operation in Jerusalem is a response to the murder of the martyr Yusuf Ramuni and to the series of crimes by the occupier at Al-Aqsa and Hamas calls to continue these operations," Hamas spokesman Sami Abu Zuhri said in a statement.
"Hamas calls for more operations like it."
Islamic Jihad echoed the comments in a separate statement.
"Islamic Jihad salutes the operation in Jerusalem which is a natural response to the crimes of the occupier," it said.