"Three members of the security forces were killed and seven people, including candidate Zineb Abdel Hamid al-Hiti, were wounded," he said.
A municipal employee today also succumbed to injuries sustained in the attack, the anonymous official said.
He said the second attacker detonated his belt shortly after the first, but did not cause any casualties.
Medical sources confirmed the death toll of four and said Hiti had been hospitalised with light injuries.
There has been no claim of responsibility for the attack, which took place in the tribal desert province of Al-Anbar, primarily home to Sunni Muslims.
Sunnis are a minority in Iraq, where more than two-thirds of the population is Shiite Muslim.
For three years, the Sunni Islamic State jihadist group ruled over the province, which stretches from the western periphery of the capital to the border with war-torn Syria.
In December, Baghdad declared "victory" against IS after retaking the groups last urban stronghold in Al-Anbar.
But according to experts, jihadists are still hiding along the porous border with Syria and in parts of the Iraqi desert.
Elections held in Iraq since the US-led invasion in 2003 and the fall of Saddam Husseins regime have all been marred by deadly violence.
But in the runup to the May 12 polls, the country has enjoyed a respite from violence which has significantly decreased in recent months.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)