Violent clashes exploded in East Jerusalem yesterday after two Palestinian cousins stormed a synagogue, killing four worshippers before being shot dead by police.

Three of the dead - Aryeh Kupinsky, Cary William Levine and Mosheh Twersky - held dual US and Israeli citizenship while the fourth, Avraham Goldberg, was Israeli and British.

East Jerusalem has seen an escalating series of killings by Israelis and Palestinians since the start of October, when Tel Aviv approved yet another colonising Jewish-only housing development in the city.

Israeli nationalists secretly bought up houses in the heart of the Arab neighbourhood of Silwan in the following week, while subsequent controversial visits to East Jerusalem's Dome of the Rock by zionists demanding access to the site further inflamed tensions.

Palestinian Authority President Mahmoud Abbas immediately condemned the attack on the mosque, saying that "civilian and religious sites should never be targeted."

But he called for an end to Israeli provocations around the Dome of the Rock and al-Aqsa mosque.

Israeli Prime Minister Benjamin Netanyahu vowed vengeance, saying he would respond "harshly" and "with a heavy hand."

Israel already systematically demolishes the homes of Palestinians whose relatives are suspected of being involved in resistance to its occupation.

Mr Netanyahu and Defence Minister Moshe Ya'alon accused Mr Abbas of deliberately inciting terrorist attacks against Israelis - but were immediately contradicted by security service Shin Bet chief Yoram Cohen.

Speaking to the foreign affairs and defence committee, he reportedly clashed with committee chairman Ze'ev Elkin, arguing that the Palestinian Authority had "no interest" in inciting terror attacks.

And he warned ministers not to seek revenge by trying to encroach on Palestinians' exclusive right to worship at the al-Aqsa mosque, considered Islam's third-holiest site but believed by many zionists to sit on the site of the Biblical Temple.

Mr Cohen told MPs that any such move would spark a "religious war," echoing Mr Abbas's own warnings in recent weeks.