Eight Palestinians have been killed in heavy fighting in the Gaza Strip that has torpedoed a truce between warring factions Fatah and Hamas as clashes spread across the territory on Friday.
Two members of the mainstream intelligence service controlled by Palestinian president and Fatah party leader Mahmud Abbas died in a shootout with Hamas gunmen in the Jabaliya refugee camp, a security source said.
Sustained clashes between militants of the rival camps were reported throughout the radicalised territory on what should have been the fourth day of a truce.
The fighting deepened as the four sponsors of the stalled Middle East peace process, the European Union, Russia, United Nations and United States, were set to meet in Washington to push a plan to fast-track their peace efforts.
US Secretary of State Condoleezza Rice is to press for renewed efforts to bolster Abbas in his power struggle with Islamist party Hamas, which won a general election last year and which the West blacklists as a terrorist outfit.
The clashes flared again after Hamas accused Washington of trying to provoke a Palestinian civil war by granting 86 million dollars to bolster Fatah security forces and claimed an Arab country had shipped arms to Fatah.
Six Palestinians were killed and another 70 wounded on Thursday, after a Hamas ambush of a presidential guard supply convoy left one guard dead on what had been the third day of a tentative truce between the two rival camps.
Presidential guards loyal to Abbas overnight occupied the Islamic University in Gaza City, a known bastion of Hamas, which took over the government in March and limited the secular Fatah party's hold on power to the presidency.
Several armed men were detained, with weapons and explosives confiscated during a sweep of the campus, a security source said.
The operation was conducted after Hamas militants hunkered down at the university fired mortar shells and rocket-propelled grenades towards the presidential compound in Gaza City.
Of the six Palestinians killed on Thursday, four were members of Abbas's presidential guard killed during the initial clashes outside the Bureij and Nuseirat refugee camps in the central Gaza Strip after the convoy ambush.
At least one of the dead belonged to a rival Hamas force, answerable to the Islamist-led government and which Abbas has slammed as "illegal".
The presidency has blamed Hamas for the latest Gaza violence, just days after the deadliest bout of internecine Palestinian violence in a year ended with 35 people dead as Arab diplomats battled to secure a ceasefire.
"The presidency strongly condemns the intentional and premeditated flare-up provoked by Hamas and its militiamen under lying pretexts," spokesman Nabil Abu Rudeina declared in a statement on Thursday.
A tentative truce had been put in place early Tuesday but was shattered when the clashes erupted on Thursday.
The presidential guard accused Hamas gunmen of setting up an impromptu checkpoint to intercept one of its convoys from Egypt that was transporting tents and equipment, confiscating two trucks.
A presidential guard spokesman flatly denied any weapons were in the convoy. The attack came after Hamas accused "an Arab country" of shipping arms to pro-Fatah Force 17 through Egypt.
Fatah denied receiving any such shipment.
The head of Egypt's Gaza-based security delegation, Burhan Hammad, dismissed the allegations as a "total lie" intended to push bitter rivals Fatah and Hamas into an "arms race".
After Thursday's fighting resumed, Hammad, who personally helped to secure the ceasefire, slammed the "unjustified aggression targeting an aid convoy for the presidential guard," and again denied it carried weapons.