Muhanad Ghazi was gunned down as he walked home from the mosque in east Mosul.
At least six candidates have now been killed in the city ahead of the June 20 elections in a total of eight attacks targeting provincial council candidates in the city and surrounding province of Nineveh.
Nineveh and Anbar, two Sunni-majority provinces in north and west Iraq, are holding the elections two months after the rest of the country after officials cited security concerns.
Sunni militants linked to Al-Qaeda often single out fellow Sunnis standing in elections for attack in an attempt to undermine confidence in the political process and intimidate voters.
Residents accuse the security forces of failing to do enough to prevent such attacks.
Iraq has been hit by several attacks targeting provincial council hopefuls ahead of the polls on April 20 in 12 provinces and yesterday in Anbar and Nineveh, with more than a dozen candidates killed nationwide.
The country has been grappling with a surge in violence since the beginning of the year, which analysts say is fuelled by discontent among the Sunni minority which alleges it is being targeted by the Shiite-led authorities.
