At least 10 people have been killed and over 40 injured in sectarian clashes in Pakistan's tribal city of Prachanar, prompting authorities to impose a curfew and issue shoot at sight orders.

Trouble started on Friday after a fight broke out between Sunni and Shia Muslims in Parachinar, the capital of the tribal Kurram Agency some 290 km west of Islamabad, according to local reports.

At least 10 people were killed and more than 40 injured when the two groups opened fire, an official said on Saturday. The Army has been called and a curfew imposed in the city.

"The army, backed by Cobra helicopters, has now taken full control of the city and firing has also been stopped," local administrator Sahibzada Muhammad Anees told Geo TV from Parachinar on phone.

He said that two helicopters hit positions of both sides from where the shots were being fired.

Anees said that the army and paramilitary have started joint patrolling, adding that there would be no relaxation in curfew.

"We have issued shoot at sight orders on Saturday and anyone trying to violate the curfew will pay the consequences," Anees said.

The fighting has also spread to adjoining areas of the city with both sides using heavy weapons, according to local reports.

A delegation of tribal elders has been sent to the area to broker a ceasefire. Thousands of people have been killed in sectarian violence in Pakistan in recent years with the majority Sunni and minority Shia sects blaming each other for it.