The National Counter Terrorism Authority on Monday had told a Senate standing committee that some leading political leaders faced death threats from militant outfits ahead of the 25 July general elections in Pakistan.
Nobody has so far claimed responsibility for the explosion.
Last month, a USA drone strike killed the Pakistani Taliban chief Mullah Fazlullah, who had claimed responsibility for most of the attacks against the ANP in the 2013 election on the grounds that it had supported military operations against the militants.
Haroon Bilour's father Bashir Ahmed Bilour was killed by a Pakistani Taliban suicide bomber in Peshawar in 2012.
The politicians facing security threats included the former Khyber Pakhtunkhwa (KP) chief ministers Jamiat Ulema Islam-Fazl (JUI-F) Akram Durrani and ANP's Ameer Haider Hoti. Peshawar is considered as a gateway to Pakistan's troubled tribal regions, from where many terror groups including al Qaeda are allegedly operated.
Militants have targeted politicians, religious gatherings, security forces and even schools in Peshawar.More news: Aunt Meghan: Duchess of Sussex stuns in green at Prince Louis’ christening
An AFP reporter saw human remains, shoes, broken chairs, and caps littered at the scene.
Pakistan's Election Commission has asked the military to help hold a "free and fair election" in the face of security threats.
This photograph taken on April 25, 2013 shows Peshawar provincial assembly candidate Haroon Bilour (2nd L) attending a meeting with party activists for the forthcoming general election in Peshawar. "I lost consciousness after the blast", he said.
Fireworks were being burst as the ANP candidate from PK 78 constituency arrived on the stage when the suicide bomber blew himself up. "The last thing I saw was a big ball of fire".
According to a tweet by Director General of Inter-Services Public Relations (ISPR) Maj Gen Asif Ghafoor, Army Chief shared grief of Bilour family and ANP on condemnable targeting of Haroon Bilour & victims of heinous terrorist attack. These groups have often targeted political parties and leaders who oppose their views.
But security across Pakistan, including in Peshawar, has dramatically improved since government and military operations in recent years.