No militant group immediately claimed responsibility for the attack but both the Taliban and the Islamic State group regularly stage attacks in the country's capital.
Multiple blasts rattled eastern Afghanistan’s Jalalabad early on Wednesday killing employees of the Afghan construction company EBE and a military intelligence officer.
A bomb exploded near a heavily-fortified foreign compound in Kabul, killing at least four people and wounding over 100.
Abed Ahmad Zia, a provincial government official, says there were fears the death toll from Friday's attack could rise further.
The Taliban quickly claimed responsibility for the attack, which takes the number of candidates killed so far during the campaign season to at least 10.
The Taliban claimed responsibility for the attack on Jabar Qahraman, who was running for the southern province of Helmand, a stronghold for the militant group.
At least nine election candidates have been killed in the lead-up to Afghanistan's long-delayed parliamentary elections on October 20.