Supporters of Tehreek-e-Taliban commander Khan Said Sajna and followers of the late TTP leader Hakimullah Mehsud clashed in the Shawal area of the troubled North Waziristan district, a security official told AFP.
Four other militants were wounded during the gunfight which was still continuing, the official said late today.
Local intelligence officials and militant sources confirmed the clash and casualties.
Earlier in the day two militants were killed in a bomb blast at a bazaar in Miranshah, the main town in North Waziristan, known as a stronghold of Taliban and Al-Qaeda linked militants.
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A militant source confirmed the attack, and said that those killed were members of the main faction of the TTP, headed by warlord Mullah Fazlullah.
No group immediately claimed responsibility for the attack, but infighting between different Taliban factions have killed dozens of people in the area recently.
Washington calls the region the most dangerous place in the world.
The latest attack comes two weeks after the Pakistani Taliban formally ended a ceasefire called to promote talks with the government aimed at ending the militants' bloody seven-year insurgency.
Since the TTP rose up against the Pakistani state in 2007, more than 6,800 people have been killed in bomb and gun attacks around Pakistan, according to an AFP tally.
Violence erupted last month between the Sajna and Mehsud factions, both part of the TTP, which has been waging a bloody seven-year insurgency against the state.
The feud began after Sajna, a senior commander, was rejected for the TTP leadership following the killing of then-leader Mehsud last November, militants say.
Sajna had been seen as a strong candidate to become TTP chief following Mehsud's death.
But the movement's ruling council at the last minute elected Mullah Fazlullah, who hails from Swat and is believed to be hiding in Afghanistan.