Another senior police official Kaukab Farooqi confirmed that the blast killed Bilour and injured 36 others.
The attack targeted a campaign event organised in the city of Peshawar by the Awami National Party, which has been targeted by Islamist militants in the past over its vocal opposition to extremist groups like the Taliban.
There was no immediate claim of responsibility for the attack.
Phone maker Xiaomi shares slip in trading debut in Hong Kong
Despite Xiaomi's challenging debut, Reuters notes that Hang Seng - the Hong Kong stock market index - was 1.7 percent higher. Others say the ongoing trade war between the US and China has spooked investors from putting money in Chinese companies.
Earlier, Pakistan's military warned of security threats in the run-up to parliamentary elections scheduled for July 25.
Mohammad Khurasani, a spokesman for the Pakistani Taliban, said in a statement that they targeted ANP's rally, killing Bilour, a candidate for a seat in the provincial legislature in Peshawar.
Following the incident, the Election Commission of Pakistan postponed the polls in PK-78 (Peshawar-XIII) constituency.
The head of Peshawar city police also informed media representatives that some 8 kilograms of explosives were used in the attack.
Local authorities said a preliminary investigation concluded that the attack was targeted on Bilour and that "a young boy blew himself up at the main entrance of the gathering when Bilour entered the venue", Dawn newspaper reports.
China counter-punches against U.S. in growing trade war
It also is rooted in the clash between American notions of free trade and Beijing's state-led development model. For the time being, analysts say it's hard to see Washington or Beijing backing down in the dispute.
Another party worker, Yaseen Khan, said a deafening explosion rocked the compound as Haroon Bilour shook hands with supporters.
Police, security forces and rescue teams rushed to the site and transported the injured to hospital.
"In solidarity with the Bilour family & ANP I've suspended my political activities for today and Peshawar jalsa which was to be held tomorrow". The ANP, which campaigns against the Taliban, has been a regular target of militants operating in Pakistan's northwest.
The attack came after the army said it would deploy more than 370,000 soldiers to polling stations - over five times more than the number deployed for the last election in 2013.
Chief Election Commissioner (CEC) Sardar Muhammad Raza denounced the attack, saying: "This shows weakness of our security institutions and a conspiracy against transparent elections".
GOP ex-Sen. Jon Kyl will be the 'sherpa' for SCOTUS nominee
Throughout the search for Trump's second Supreme Court nominee, Kavanaugh was a favorite of the conservative legal cognoscenti. With Kavanaugh , Trump is replacing a swing vote on the nine-member court with a staunch conservative.