Earlier on Thursday, thousands of Palestinian security men fired automatic rifles and vandalised the parliament in Gaza in one of the biggest protests over unpaid wages since the Hamas government took office in March.
Medics and a security official said Khader Afana, a Fatah member of the preventative security force, was killed by unknown gunmen in Gaza City. No one claimed responsibility for the shooting.
In further violence on Thursday, three more security officers were wounded as their vehicle was attacked in a village east of the town of Khan Younis, the security official said, accusing Hamas of the ambush.
Hamas said the Fatah fighters fired at one of its senior commanders, which prompted them to return fire. A Hamas gunman was slightly hurt in the exchange.
Witnesses and medics said a further three Fatah members were lightly wounded in a gunbattle between Fatah and Hamas gunmen in Khan Younis early on Thursday.
Palestinian security men earlier fired shots at the parliament building in Gaza in one the biggest protests over unpaid wages since Hamas formed a government in March.
The protest was staged while parliament was in session. Ahmed Bahar, a Hamas politician, condemned the attack and said protesters vandalised the building's reception area, electronic equipment, doors and air-conditioning units.
About 70,000 security men are on the government payroll and most of the protesters were Fatah supporters loyal to Mahmoud Abbas, the president.
They were seen by witnesses climbing on to the roof and smashing windows, but no one was hurt and the crowd dispersed after about three hours.
"We want to know when this tragedy will stop," one security official shouted through a loudspeaker outside parliament.
The government has been unable to pay 165,000 government workers for three months because of an aid boycott by the United States and other Western countries.
The protest comes after Tuesday's pledge by Ismail Haniyeh, the prime minister and leader of Hamas, to make partial payments to employees of the Palestinian Authority in the next few days.
A full month's wages will be paid to 40,000 workers whose monthly salaries are less than 1,500 shekels ($330), while the other 125,000 government workers, who earn more, will get advances of the same amount.
"The 1,500 shekels are not enough to pay debts, buy milk and diapers," said one banner stuck to the gate of parliament.