"Maulana Sami-ul-Haq has been killed", he said from outside the government hospital where his body was taken.
Maulana Samiul Haq, who was also famous as the "Father of Taliban" in Afghanistan, was stabbed to death in his residence.
Earlier reports had emerged suggesting that Maulana Samiul Haq was shot dead by gunmen riding a motorcycle.
A security guard of Sami ul Haq also has sustained serious injury, the report said.
Haq was known as the father of the Afghan Taliban due to the huge influence and respect he enjoyed among the leaders and cadres of the militia.
Speaking to the television channel, Hamidul Haq said Maulana Samiul was unable to participate in the protests against Asia Bibi's acquittal by the Supreme Court in a blasphemy case.
The prime minister's aide on political affairs, Naeemul Haq, said the religious scholar's martyrdom was a huge tragedy.
Minister of State for Interior Shehryar Afridi has also condemned the assassination.
The family of the religious scholar and the Jamiat Ulema Islam-Sami (JUI-S) officials confirmed the news of his assassination.
Sami ul-Haq, who was in his 80s, ran an Islamic school in Khyber Pakhtunkhwa Province in Pakistan's northwest.
Afghan Taliban spokesman Zabiullah Mujahid said the "people of Afghanistan will never forget (Haq's) services for them" and his killers were the "enemies of Islam". He formed Muttahida Deeni Mahaz (United Religious Front), an alliance of relatively small religio-political parties, to participate in Pakistani general election, 2013.