Negotiations

"At the moment there are negotiations with the three Hamas fighters to surrender, to give themselves up," she said. 

"We know that one of the mothers of these fighters came to try and mediate her son's surrender, [but] the Hamas fighters have so far refused.

"Other efforts are undergoing as well to surrender the body of the Palestinian officer who was killed, but so far all of these efforts have not yielded any positive results and the clash is continuing."

The fighting was the latest in a series of incidents that have further stoked tensions between Abbas' Fatah movement and Hamas, which controls the Gaza Strip.

Earlier this week, three police officers, two Hamas fighters and a bystander were killed in fighting in Qalqilya, following a dawn raid on suspected Hamas members.

The raid sparked angry demonstrations by Hamas supporters in the Gaza Strip.

Hamas says that Fatah-dominated security forces are pursuing a politically motivated crackdown against Hamas activists, a claim which Fatah has also made about Hamas in Gaza.