The accident took place in the Bala Nari area of Sibi district, Police official Muhammad Amjad told reporters.
"They were coming from opposite directions and apparently the drivers lost control and the bus fell into a ravine," he said.
The injured were rushed to civil hospital Sibi for medical treatment.
Both vehicles were severely damaged during the accident.
Amjad said while six people died on the spot, four others succumbed to their injuries while being rushed to hospital.
In March, two passenger buses collided with a oil tanker in which at least 35 people were killed.