Unknown attackers killed the prominent cleric, who runs an Islamic school in northwestern Pakistan, his deputy Yousaf Sha and nephew said.
Pakistani police and the family of prominent cleric Maulana Sami ul-Haq, who also was known as the "father of the Taliban," say he was killed outside his home in Rawalpindi.
Unknown attackers killed the cleric, who runs an Islamic seminary in northwestern Pakistan, his deputy Yousaf Shah said.
There were conflicting reports of exactly how he was killed and why his bodyguard and driver were apparently not there to defend him at the time of the attack.
Shah initially said that Haq had been shot dead.
Haq's nephew Mohammad Bilal said that his uncle was found with stabbing and gunshot wounds in a house he owns in an upscale area on Islamabad's outskirts.
"When the assailants entered his house ... They first started stabbing Maulana Sami ul-Haq with knives and daggers and then shot him dead," he said.
Further details remained unclear.
TRT World's Ali Mustafa reports.
Shah said the attacker's identity and their motive were not immediately known. Haq was the head of his faction of the Jamiat-e-Ulema Islam party.
Haq has run the Darul Uloom Haqqania seminary in Pakistan's Khyber-Pakhtunkhwa province, near the Afghanistan border, for decades.
One of his students from the 1980s, known later as Mullah Mohammad Omar, went along with classmates to Afghanistan to join mujahideen groups fighting against the Soviet occupation of the country.
Mullah Omar went on to found the Taliban, which seized power in Afghanistan in 1996 after years of chaos and civil war following the Soviet military's withdrawal.
Haq's seminary has continued to thrive in Pakistan, including being allocated funding in provincial government budgets.
Pakistan's Interior Ministry confirmed Haq's death in a statement on Friday evening, and expressed condolences.