He was shifted to the Safari Hospital in Rawalpindi for medico-legal formalities.
Haq's son Maulana Hamidul Haq confirmed his death in the attack. "He returned to his house and was resting in his room", he said.
"Upon returning to the room, the driver found Maulana Samiul Haq dead in his bed and his body covered in blood", he said.
Pakistani police and family of a top cleric Haq who was known as "father of the Taliban" has been killed in a knife attack in his bedroom at home in the garrison city of Rawalpindi.
The prime minister said Maulana Samiul Haq was a great scholar of Islam.
The prime minister has sought a report and directed that an investigation be carried out immediately to find those responsible.
The report said gunmen riding on motorbikes opened fire on Sami ul Haq's vehicle and as a result he was injured and then died.
"With Maulana Sami-ul-Haq's martyrdom, the country has lost an important religious and political leader", he said on Friday.
Minister of State for Interior Shehryar Afridi has also condemned the assassination. In a statement, he said Maulana Sami-ul-Haq s political and religous services will be remembered.
Maulana Samiul Haq, who was also famous as the "Father of Taliban" in Afghanistan, was stabbed to death in his residence.
Many of them attended his Haqqania seminary, a well-known Islamist school in northwest Pakistan on the border with Afghanistan. There he studied fiqh, usul al-fiqh, Arabic literature, logic, Arabic grammar (sarf and nahw), tafsir, and Hadith.
He was a religious scholar and former Senator.
He has twice been a member of the Senate of Pakistan from 1985 to 1991 and again from 1991 to 1997.
Maulana Sami, said to be around 82 years old, was the head of the Darul Uloom Haqqania seminary in Khyber Pakhtunkhwa's Akora Khattak. Samiul Haq was also a founding member of Muttahida Majlis-e-Amal.