The government began a belated investigation after a human rights group broke the story, The Times of London reported Friday. The group said that the teenagers, aged 18, 16 and 14, were tortured, shoved into a ditch and buried under sand and stone.
An autopsy found that the skulls of two of the victims were fractured before they were buried.
The older women were described as the aunt of one victim and the mother of another who were also buried when they tried to stop the violence.
The killings reportedly took place on July 13 near the village of Baba Kot in Baluchistan.
The victims allegedly became targets because they were determined to marry men of their own choice. Those arrested include the father of one victim and brothers of the others.
The Human Rights Commission of Pakistan says that 636 honor killings were reported in 2007. In one incident, an adulterous couple was stoned and beaten and in another two young women were killed after being dragged through their village.