Employees of the Independent High Electoral Commission tally votes at a counting station in Baghdad. (Ahmed Jadallah/Reuters)

The top United Nations envoy in Iraq says preliminary results from Sunday's election will likely not be released until Thursday as a result of a "very complicated process" in counting ballots.

UN diplomat Ad Melkert urged Iraqi election officials to release the results of the historic vote as quickly as possible, saying Iraqis "have the right to know as soon as possible what is the outcome of their choice."

Faraj al-Haidari, the head of Iraq's Independent High Electoral Commission, said vote counters were entering results into the computer and that updates on that process might be ready on Wednesday. But a senior member of the panel, Qassim al-Aboudi, said the first results likely would come Thursday.

The poll's complicated ballot contains some 6,200 candidates competing for 325 parliamentary seats.

62% of voters cast ballots

Al-Haidari said about 62 of eligible voters cast a ballot in the election, defying a wave of insurgent attacks aimed at disrupting balloting.

The turnout is expected to be less than in nationwide elections in December 2005, when about 76 per cent of eligible voters cast ballots.

Prime Minister Nouri Al-Maliki, who campaigned as the head of his State of Law Coalition as the best candidate to ensure security, faced challenges from both former premier Ayad Allawi and a coalition of conservative Shia parties, including one led by popular anti-American cleric Muqtada al-Sadr, who did not run himself.

Whichever group forms the next government will largely set the course for Iraq, as U.S. combat troops are expected to withdraw from the country in 2011, over eight years after they led the 2002 invasion that helped overthrow the government of Saddam Hussein.

With files from The Associated Press