Baghdad, March 7 (DPA) Four people were killed and 11 injured Sunday in two blasts in Baghdad, as Iraqis headed to the polls amid heavy security to cast their votes in the parliamentary elections.

Four people were killed and eight injured when an improvised explosive device detonated in the al-Shurta al-Rabea area, a police source was quoted by the Aswat al-Iraq news agency as saying.

Another three civilians were injured when a mortar fell near an electoral centre in Baghdad's western neighbourhood of Dragh, added the source.

The heavily guarded Green Zone was hit by four mortar shells, police sources and eyewitnesses told DPA.

Explosions were heard in the al-Khadra district of western Baghdad and the al-Bonouk district of eastern Baghdad, sources added, without giving further details.

Iraqi authorities imposed a curfew from Saturday night until 5 a.m. March 8, which restricts movement of vehicles and closes air, land, and sea ports.

Over half a million members of Iraqi security forces are working to maintain peace during the elections.

The weeks leading up to voting were fraught with sectarian and political violence, as well as a large number of attacks targeting Iraqi security forces.

In Basra city, in south-eastern Iraq, Iraqis headed to the polls in a more calm atmosphere. Roses and sweets were distributed to people after they cast their votes.

The Iraqi Independent High Electoral Commission says it expects some 18.9 million Iraqis to cast their votes. Over 500,000 local and international observers are monitoring the election process.

Nearly 6,300 candidates are competing for 325 seats in parliament, making it the largest parliamentary election in Iraq's history.