Earlier results, based on a 95 per cent tally of ballots, showed al-Maliki's mainly Shia bloc facing a virtual tie with the alliance led by Allawi, who has garnered heavy Sunni support.

Al Jazeera's Anita McNaught reporting from the Iraqi capital, Baghdad, said: "No one can tell in this very complex electoral calculation process exactly how things will pan out; until you have the final figures you can't do the seat allocations.

"All we know is that it is neck-and-neck between al-Maliki and Allawi."

Fears of violence

special report
  Iraq election tally so far
  How the electoral system works

The close race has raised tensions in Iraq after an election voters had hoped would offer stability after years of sectarian warfare.

The tensions foreshadowed potentially divisive talks to form the next government.

The close race also sets the stage for protracted political wrangling over forming a new government that could spark new fighting and complicate US efforts to speed up troop withdrawals in the coming months.

Sectarian violence increased when politicians took more than five months to agree a government after the last parliamentary vote in 2005; tens of thousands of people were killed.

Voter 'irregularities'

All of the major parties have alleged irregularities in the election. However, Maliki and his supporters have been particularly outspoken since the last published results put Allawi's bloc ahead in the national count by about 11,000 votes.

Iraq's IHEC will announce full results, despite calls for a delay amid fears of violence [EPA]

Foreign diplomats and analysts have expressed concern about the possibility of renewed violence if the losing parties refuse to accept the results.

Violence has dropped dramatically in the last two years but attacks blamed on Sunni fighters occur daily.

Major General Qassim al-Moussawi, Baghdad's security spokesman, said security forces were not imposing a curfew but would be ready for any signs of trouble as the vote results are being released.

"We have a heavy deployment of troops in all areas, checkpoints, to reassure people and address their concerns," he said.