An Iraqi police official says a car-bomb blast in the holy city of Najaf killed at least three people and injured more than 50. The official says the blast occurred Saturday near a bus carrying pilgrims, killing one Iraqi and two Iranians. The official spoke on condition of anonymity because he was not authorized to speak to media. Director Radwan al-Kindi of the Najaf Health Department confirmed the deaths. The blast comes a day before Iraqis vote in key parliamentary elections. Blasts in other Iraqi cities have killed dozens this week. U.S. and Iraqi officials have warned that insurgents could attempt to disrupt the vote with violence. Najaf lies 100 miles (160 kilometers) south of Baghdad. It holds important Shiite shrines and has close religious ties with neighboring Shiite power Iran.