At least 54 others - 17 Iraqis and 37 Iranians - were injured in the attack near the Imam Ali Holy Shrine, which houses the tomb of Ali, cousin of the Prophet Mohammed.

Iraqis go to the polls on March 7 to choose a 325-member parliament. The election has been marred by violence despite heavy security.

It is Iraq's fifth nationwide vote since 2003, but only the second for a full four-year-term parliament.

Sunday's elections were supposed to happen in January but were delayed because of political disagreements and a delay in passing the election law that paved the way for this vote.

There are 18.9 million eligible voters, casting ballots for 325 seats in the Council of Representatives, as Iraq's parliament is called. The seats represent Iraq's 18 provinces. At least a quarter of the positions - 82 - are guaranteed to go to women, and eight more have been allocated for minorities. They include five set aside for Christians and one each for the Shabak, Sabaeans (Mandaeans), and Yazidis.