The authorities imposed a curfew in Gilgit on Saturday, the main town in the mountainous region known as the Northern Areas, and called out the army to quell the violence after enraged Shia went on the rampage following the attack on Ziauddin Moosavi.
Moosavi was travelling in his car to a mosque in the centre of Gilgit, about 240km north of the capital Islamabad, when unidentified gunmen opened fire on him, critically injuring him and his three guards.
Two of the guards later died.
One of the attackers was killed when Moosavi's guards returned fire, Northern Areas Home Secretary Jamil Ahmad said.
"He is not from Gilgit. We are trying to establish his identity," he said.
"People are very terrified"
Ahmad said eight people were killed in the violence that followed the attack on Moosavi.
An angry mob set fire to the house of a forest department official, burning alive the official and five others. A local health department official was also attacked and killed.
Witnesses said angry mobs also set government buildings and cars on fire. "People are very terrified," a resident said.
No one claimed responsibility for the attack on Moosavi but police suspect it was a sectarian incident.
Attacks by members of Pakistan's majority Sunni and minority Shia Muslim communities have killed hundreds of people over the years.
Saturday's violence was the worst in Gilgit since June, when one man was killed in clashes between security forces and Shia protesting against the school curriculum.
Shia account for 15% of Pakistan's 150 million population.