It is unclear if the fighting will weaken an insurgency aimed at bringing down the nuclear-armed Pakistani state, but the security agencies will be hoping to turn it to their advantage.
The violence is between rivals in the Mehsud tribe, one of numerous ethnic Pashtun groups that straddle the Afghan-Pakistan border who have for generations battled outsiders to preserve their autonomy.
The Pakistani Taliban, a loose alliance of militant groups drawn largely from Pashtun communities, has been fighting for years to overthrow the government and impose Islamic law.
The rivals are from the same sub-group of the Mehsuds, a tribe based in the South Waziristan region that provides the Taliban with the bulk of its money and many of its fighters.
On one side is a commander called Khan "Sajna" Said, who acts as an arbitrator for the Taliban in the city of Karachi and controls lucrative extortion rackets there, according to an analyst with extensive contacts in the insurgency.