The murder happened last week in the town of Donga Gali, about 50km northeast of the capital, Islamabad.
The 'honor killing' was ordered by the tribal elders as punishment after the victim, identified as Ambreen, helped a couple to escape from the village of Makol to elope.
It is said that the couple violated tribal norms by running off together.
Police officer Khurram Rasheed told reporters, "The order came after Ambreen's neighbor, Saima, eloped with her boyfriend on the 22nd of April."
“The elders took her to an abandoned place outside the village and rendered her unconscious by injecting her with some drugs," said another police officer.
"Then they seated the girl in the van in which the couple had escaped. They tied her hands to the seats and then poured petrol on her and the vehicle," he added.
Fifteen members of the tribal council, including the victim's mother and brother, were arrested for the murder.
An honor killing is the homicide of a member of a family or social group by other members, due to the belief the victim has brought dishonor upon the family or community. It is typically carried out against a woman or girl, although men may also be killed.
Around 1,100 women were killed by relatives in Pakistan last year, although tribal councils have no legal power in Pakistan.
Human right groups also reported in 2011 that 720 honor killings, including 605 women and 115 men, occurred in Pakistan.
