BAGHDAD: A roadside bomb killed an Iraqi provincial elections candidate and three other people north of Baghdad on Sunday, bringing the number of candidates killed in attacks to 14, officials said.

Najm al-Harbi was on travelling to Baquba on a highway in Diyala province in his personal vehicle when the bomb exploded, killing him, two of his brothers and a bodyguard, a police lieutenant colonel and a doctor said.

An official from Deputy Prime Minister Saleh al-Mutlak's office confirmed Harbi's death, and said he was the head of the deputy premier's list in Diyala province.

Harbi's killing comes a day after Hatim Mohammed al-Dulaimi, a candidate for Salaheddin provincial council, was shot dead by gunmen near his home in Baiji, north of the Iraqi capital.

Soldiers and policemen cast their ballots for the provincial elections on Saturday, a week ahead of the main vote, the country's first since March 2010 parliamentary polls.

The election comes amid an uptick in violence and a long-running political crisis between Prime Minister Nuri al-Maliki and several of his erstwhile government partners.

The credibility of the elections has been drawn into question following deadly attacks on candidates and a government decision to partly postpone voting that means only 12 of Iraq's 18 provinces will take part.

More than 8,000 candidates are standing in the elections, with 378 seats on provincial councils up for grabs. An estimated 16.2 million Iraqis are eligible to vote, among them about 650,000 members of the security forces.

Although security has markedly improved since the height of Iraq's confessional conflict, 271 people were killed in March, making it the deadliest month since August, according to AFP figures.