Palestinian police, searching for weapons, clashed with gunmen in the city of Shechem (Nablus) late Thursday night, leaving four people dead, Palestinian officials report.
The firefight erupted on Thursday evening after officers entered Shechem's Old City, a densely populated warren of alleyways that was one of the flashpoints of the Second Intifada between 2000 and 2005.
The shooting was still continuing on Friday morning, security forces spokesman Adnan al-Damiri said.
Shechem governor Akram Rajub said that two police had been killed in the operation as well as two gunmen, both of whom he said were on a police wanted list.
The area has seen a number of Palestinian police raids in recent months, due factional infighting within the ruling Fatah movement of Palestinian president Mahmud Abbas.
AFP contributed to this report.