Footage showed volunteers and police rushing the wounded to hospital.
The attack on a meeting of the Awami National Party (ANP) in Peshawar also injured almost 50 others, city police chief Jamil Qazi said.
"Sad to learn of Haroon Bilour and 2 other ANP workers deaths and strongly condemn the terrorist attack at the ANP corner mtg in Peshawar".
Bomb disposal squad chief Shafqat Malik said eight kilos of TNT explosive was used in the blast.
The deceased ANP candidate, who was set to contest the July 25 elections from Peshawar's PK-78 constituency, will be buried in Wazir Bagh at 5pm today (Wednesday). Bilour suffered serious injuries and was shifted to the hospital where he succumbed to his wounds. Earlier in July, seven people including a candidate of the Muttahida Majlis-i-Amal, a gathering of religious parties were injured in an explosion during an election rally near Takhtikhel also in the KPK province. After being informed, rescue teams, police and ambulances rushed to the crime spot and investigation is underway.
The blast occurred as Haroon Bilour arrived at the stage to address supporters in Yaka Toot area.
19 injured, 1 dead in South Africa plane crash
Police spokesman Isaac Mahamba told South African broadcaster eCNA: "There is smoke all over and paramedics are on the scene". Eyewitnesses described seeing the plane attempt to veer toward Wonderboom airport, then hearing an 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 operations against the militants.
Tuesday's attack came hours after the military said it would deploy more than 3,70,000 security forces to polling stations to ensure free, fair and transparent national elections on 25 July.
Haroon Bilour teenaged son Danial Bilour was among the injured.
They have often been claimed by the Pakistani Taliban and their allies.
Last month, a United States 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.
Officials said at least 54 people were wounded.
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