Four people were killed as clashes erupted in Gaza between forces loyal to Palestinian President Mahmoud Abbas and the Hamas government in the worst bout of fighting since the rivals agreed a fragile truce two weeks ago.
At least 10 people were wounded in separate incidents across the Gaza Strip, hospital officials said.
Abbas' Fatah faction and Hamas declared the ceasefire in the wake of violence that escalated after Abbas called for early elections to break a political deadlock with the Islamists.
Hamas condemned Abbas's move as a coup to oust it less than a year after it surprised Fatah to win a parliamentary ballot.
The fresh violence is likely to revive fears among Palestinians that Gaza could slip into civil war.
Among the dead were two security officials loyal to Abbas who were killed in the southern town of Khan Younis.
Abbas' security force said the two were killed and another critically wounded when a Hamas police unit ambushed two of its vehicles. Hamas said the security force fired first.
In the Jabalya refugee camp in northern Gaza, one woman was killed after getting caught in the crossfire of a fierce clash between rival forces. Nine others were wounded, mostly combatants, hospital officials said.
That clash came after unknown gunmen killed a member of Abbas's Fatah faction who was on a rooftop in the town of Beit Lahiya and a car carrying Hamas security officers was ambushed.
Two policemen were wounded in the ambush, one seriously, the Hamas police force said.
Gunmen also abducted four Fatah members from the streets, witnesses said. Fatah blamed Hamas, which declined to comment.
While Abbas has called for fresh parliamentary and presidential elections, he has left the door open to talks with Hamas on forging a unity government that Palestinians hope will lead to the lifting of Western sanctions imposed on the Hamas administration.
Abbas has not set a date for elections. Hamas says early polls would be illegal.
