Over a dozen Palestinian militant groups Thursday pledged to step up joint and separate attacks on Israeli targets to foil Israeli-Palestinian peace negotiations in Washington.

'The factions agreed that all means are open to the Palestinian resistance to deal with Israel in the coming phase,' Abu Obaida, spokesman of the Hamas armed wing, read a statement of the Gaza-based groups in a press conference held in the Gaza Strip.

Armed groups, including the Islamic Jehad movement, the Popular Front for the Liberation of Palestine (PFLP) and the Democratic Front for the Liberation of Palestine (DFLP), who participated in the conference, blamed the Palestinian leadership for accepting the negotiations without an Israeli commitment not to continuing Jewish settlement in the occupied Palestinian territories, Xinhua reported.

Hamas militants Tuesday killed four Israeli settlers near the West Bank city of Hebron. The next day, Hamas claimed responsibility for another drive-by shooting in which two Israelis were injured near Ramallah.

The factions met Aug 30 'and agreed to bring the Palestinian resistance into an advanced phase of high-level coordination for effective work against Israel,' Obaida said.

'The escalation comes to reject all shameful projects that include dangerous concessions and to stand against all conspiracies that target the Palestinian rights through playful negotiations,' he added.

The statement also called on the Palestinian National Authority (PNA) to stop cracking down against Hamas supporters, the number of whom have increased in the wake of the attacks on the settlers. Hamas said that up to 550 supporters had been arrested during the last couple of days.