Two Palestinians were killed and 40 wounded as infighting between rival Fatah and Islamic Hamas militants renewed in the southern Gaza town of Rafah.
The two groups clashed on Saturday night as leaders of Palestinian factions were negotiating in Cairo to agree on a permanent internal cease-fire.
According to eyewitnesses clashes are still going on.
Violence between the rival groups restarted, as Hamas militants and members of the Hamas-led interior ministry auxiliary force seized roofs of several buildings in the neighborhood, said the eyewitnesses, adding Fatah militants had also blocked the roads with sand barriers and stones.
Each had accused the other of breaching the cease-fire agreement reached on Thursday.
Senior Egyptian security mediators had interfered on Thursday and managed to contain the infighting.