Haq, the 82-year-old cleric who was also known as the 'godfather of Taliban', was stabbed to death by unidentified attackers at his residence in the garrison city of Rawalpindi on Friday.
Thousands of people, including National Assembly Speaker Asad Qaiser, Governor Khyber-Pakhtunkhwa Shah Farman, Chief Minister Mehmood Khan, attended Haq's funeral prayers which were led by his son Maulana Hamidul Haq.
After the prayers, Haq was buried close to his father's grave in the Darul Uloom Haqqania. The provincial government has declared a day of mourning.
The funeral was also attended by members of political parties, religious scholars and lawmakers. A 65-member Afghan delegation also attended the funeral prayers.
Elaborate security measures were adopted with police deployed at different points in and around the Darul Uloom Haqqania. Haq was the head of the Darul Uloom Haqqania seminary, which is dubbed in the western media as "University of Jihad" as several top Afghan and Pakistani Taliban leaders studied there, including Mullah Omar who had received an honorary doctorate from the seminary.
Haq was also chief of Jamiat Ulema-e-Islam (JUI-S) religo-political party which was an ally of the ruling Pakistan Tehreek-e-Insaf (PTI) party headed by Prime Minister Imran Khan.
The slain cleric was elected twice as a member of parliament.
So far, no outfit has claimed the responsibility of the killing.
A probe has been launched to nab the assailants who apparently escaped on a motorbike, police said.
An FIR lodged at Airport Police Station of Rawalpindi showed that the attacked took placed at 6.45 pm and the octogenarian leader was stabbed 12 times in stomach, chest, forehead and ears.
The FIR was lunched as the behest of his son Hamidul Haq who told police that his father was alone at the time of attack.
The son reportedly refused to get autopsy of the cleric declaring it against teaching of Islam.
Meanwhile, police detained the driver and gunman of Haq for interrogation.
A spokesman for the Rawalpindi Police said the police had obtained CCTV footage.
Sources said that preliminary probe showed that at least two attackers were involved in the murder.