Pakistan opened an investigation Monday into the alleged murders of five women who sought to arrange marriages on their own after the brutality of the crime and foot-dragging by authorities sparked national outrage. The victims were shot, thrown in a ditch and buried alive more than a month ago. The incident allegedly occurred last month in Baba Kot, a remote village in Jafferabad district, after three teenage girls and two female relatives decided to defy tribal elders and ask a civil court to carry out marriages. Human rights groups say the victims were abducted at gunpoint by six men, forced into a vehicle and taken to a remote field, where they were beaten, shot and then covered with rocks and mud even though they were still breathing. It took so long to investigate, rights groups allege, because members of a powerful political family in the province were involved in the killings. Parliment members demanded Monday that the perpetrators be brought to justice - but only after a Baluchistan lawmaker Israr Ullah Zehri defended the practice last week as a "centuries-old tradition." That sparked fierce debate and outrage among fellow legislators. The highest court in the province immediately ordered an inquiry.