The new death brought the Palestinian death toll from the fighting in the last three days to more than 22.
Laila El-Haddad interviews members of armed groups allied to Hamas and to Fatah to discover why they do what they do - read An eye for an eye in Gaza
The streets of Gaza City were empty on Saturday after the previous day's fighting and shops and markets remained closed.
But Fatah and Hamas clashed again near the Islamic University, killing at least four in some of the fiercest fighting since Hamas's election victory a year ago.
One of the dead was believed to be a university student who was caught in the crossfire, witnesses said. Several people were also injured in the clash.
A member of the Hamas-led police force died of his wounds overnight, hospital officials said, bringing the toll from Friday's factional fighting to 18.
In the latest of a string of tit-for-tat abductions, four members of a security force loyal to Fatah, including Abed Abdeen, a local commander in the southern Gaza Strip, were taken captive by unknown fighters.
Abdeen's relatives later said that seven Hamas men in the southern town of Khan Younis had been seized in retaliation.
Hamas mounted an overnight raid on the Gaza headquarters of the Preventive Security Service, a force dominated by Fatah members, who are loyal to Mahmoud Abbas, the Palestinian president.
"It is pitiful to witness the bloody scenes in Gaza between the brothers"
Hamas attacked the compound with mortars and rocket-propelled grenades but no injuries were reported.
Grenades were also fired at the home of Rashid Abu Shbak, an Abbas loyalist in charge of internal security in the Palestinian Authority. It was unclear whether Shbak was home at the time, but no injuries were reported.
Fighting also took place outside the homes of Abbas and Mahmoud al-Zahar, the Hamas foreign minister. Hamas officials said al-Zahar's home was damaged by two rocket-propelled grenades.
|Meshaal, left, and Abbas pledged to curb |
Palestinian factional fighting [EPA]
Hamas has said any new elections would amount to a coup.
It has struggled to govern since taking office in March under the weight of sanctions imposed because of its refusal to recognise Israel, renounce violence and abide by interim peace deals.
Abbas and Khaled Meshaal, the leader of Hamas, pledged a week ago to curb Palestinian bloodshed after inconclusive talks to end their power struggle and form a unity government.
Abbas, currently in Madrid, has said he will push ahead with his plan to call early elections if coalition negotiations fail within two to three weeks.
The Arab League has expressed its "regret and discontent at the assassinations and kidnappings on the Palestinian front which could lead to dire consequences."
"It is irrational and unacceptable that the Palestinian factions are distracted from freeing the occupied territories by plunging into deadly infighting which benefits only the Israeli occupation forces," Hisham Yussef, the secretary-general's chief of staff, said.