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.
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.
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.
Iranian girl detained for posting dance videos , twitter erupts with outrage
Another person, Masih Alinejad , posted a video of herself defiantly dancing in a public park in Tehran. Last Friday, she and other detainees, whose identity could not be confirmed, appeared on Iranian TV.
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".
Tropical Storm Chris continues to spin off North Carolina coast
Big waves from a hurricane are rare in July in Nova Scotia, said Pete Cove, general manager of the East Coast Surf School. Weather officials said in a release that the storm could produce heavy surf and create life-threatening rip currents.