By Avi Issacharoff, Haaretz Correspondent and Reuters

A security officer belonging to the Palestinian Fatah faction was pushed off the roof of a 15-story building to his death in Gaza City, security officials said, hours after gunmen from rival Hamas and Fatah factions engaged in deadly gunbattles in the southern Gaza town of Rafah on Sunday.

Mohammed Sweirki, 25, who served in the Fatah-linked Presidential Guard, was kidnapped earlier by Hamas gunmen near the apartment building from which he was later pushed. His death set off skirmishes in several parts of the city.

Fatah gunmen killed a Hamas mosque preacher after shelling his house in Gaza City. Hamas threatened to retaliate. At least 11 people were wounded in the fighting, medical officials said.

The kidnapping of Sweirki and several other Fatah men sparked a brief clash between the Fatah and Hamas gunmen in Gaza City earlier Sunday. Masked gunmen, believed to be from Hamas, stopped a car carrying Fatah men and detained them for questioning. Fatah forces rushed to the area, and briefly exchanged fire with the Hamas members.

The officials said no one was wounded. Ther is no word on the fate of the other detainees.

In Rafah earlier, hundreds of rival gunmen took up positions on street corners and rooftops, pounding each other's positions with rocket-propelled grenades and machineguns.

Two men from Fatah and one from Hamas were killed, hospital officials said.

Of the more than 39 Palestinians wounded in the fighting, at least nine were in critical condition, the hospital said. The number of wounded overwhelmed the local hospital, forcing officials to send people to neighboring towns for treatment.

Tensions have remained high in Gaza since an Egyptian-brokered ceasefire took effect in mid-May. Some 50 Palestinians died in internal fighting last month alone.

An estimated 616 Palestinians have been killed in factional fighting since Hamas defeated Fatah in elections in January 2006, a leading Palestinian rights group said in a report released Wednesday.

Egyptian officials have been holding talks in Cairo with leaders from both factions but no agreements have been reached