Fatah sources said the gunfight in northern Gaza began when members of a Hamas police unit attacked the house of a senior Fatah official. Hamas said its forces were shot at first.

In the West Bank, three senior Hamas officials were attacked by unknown assailants. Bashar Karmi, the deputy health minister, was kidnapped but then released five hours later, security officials said. A second official had his car burnt and shots were fired as a third left a mosque.

"If Hamas keeps doing what it is doing with its militia in Gaza, and is killing our members, all Hamas leaders in the West Bank are in our hands''

- Jamal Tirawi, a Fatah politician
Jamal Tirawi, a Fatah politician, said that Hamas leaders in the West Bank could be attacked again.

"If Hamas keeps doing what it is doing with its militia in Gaza, and is killing our members, all Hamas leaders in the West Bank are in our hands,'' he said.

Earlier on Thursday, five people were wounded in two separate incidents as a funeral procession was held for three Fatah loyalists killed in fighting on Wednesday. A total of five people died in the violence.

In the Mughazi refugee camp, Fatah said the funeral came under fire from a building housing a Hamas kindergarten and mosque. Hamas said mourners had vandalised the mosque, but denied that its forces opened fire on the procession.

Two people were hurt. Nearby, three Fatah loyalists were wounded as they passed by a Hamas-manned checkpoint, hospital officials said.

Wednesday's fighting was the worst between the two sides since they agreed a ceasefire two weeks ago.

The factional fighting began after Abbas called for early parliamentary and presidential elections after unity government talks failed. Hamas has called the move a coup less than a year after it took power.