Five Palestinians were killed during the day as factional tensions in Gaza led to renewed outbreaks of fighting.
Gunmen killed three Fatah-allied security officials in Khan Younis, while a Fatah man died in north Gaza.
Clashes also broke out in Jabaliya where a woman was fatally caught in the crossfire and several people were hurt, hospital officials said.
There are fears the violence could undermine a fragile truce between the Fatah and Hamas factions.
The security officials were attacked by the unidentified gunmen near the town hospital, according to Palestinian security officials quoted by AP news agency.
Before the ambush, the officers reportedly stormed a house where they believed a colleague who had been kidnapped was being held.
Two died outright while one died later of his injuries, doctors said.
In an earlier incident on Wednesday, a Fatah man died in northern Gaza.
Fatah alleged he had been shot from a nearby rooftop by a Hamas sniper. Hamas denied having anything to do with the man's death, but it said that soon after the incident Fatah gunmen attacked one of its bases, injuring four people.
In the Jabaliya refugee camp, one woman was killed when she was caught in the crossfire between rival forces, Reuters news agency reported.
Several other people, mainly fighters, were injured, hospital officials were quoted as saying.
Relations between the two parties have always been bad, but they have worsened significantly in recent months as political differences have deepened, the BBC's Alan Johnston in Gaza says.
The tension exploded into days of street fighting in December, but the truce was agreed about a fortnight ago.