The BBC reports that partial results are now in from all 18 provinces, and Nouri al-Maliki has strengthened his lead over main rival Iyad Allawi.
His State of Law coalition is leading in seven provinces, including Baghdad and Basra. Baghdad is the largest constituency, with 70 seats from the total of 325.
The Iraqi National Alliance (INA) is ahead in five provinces, including oil-rich Kirkuk, where Kurdish parties were expected to win.
Mr Allawi's Iraqiya, a secular Shia-Sunni alliance, is currently in third position.