The recount due to suspicions of electoral fraud, however, would not significantly affect the overall outcome, according to experts on Iraqi politics.

The court ruled that parliament's decision on June 6 to order a manual recount in response to allegations of irregularities did not violate the constitution, its chief justice Medhat al-Mahmud told a news conference.

All of the roughly 11 million ballots, including those of voters living abroad, displaced persons and security forces, must be recounted, he said, referring to the three categories whose results MPs had decided to annul because they were allegedly the most suspect.

Last month's ballot was won by cleric populist Shiite cleric Moqtada Sadr's electoral alliance with communists, as long-time political figures were pushed out by voters seeking change in a country mired in conflict and corruption.

The result was contested -- mainly by the political old guard -- following allegations of fraud in the election, Iraq's first since the defeat of the Islamic State (IS) group.

According to intelligence services, tests of electronic voting machines -- used for the first time in Iraqi elections -- produced varied results, appearing to give credence to the fraud claims.

The vote saw a record number of abstentions as Iraqis snubbed the corruption-tainted elite that has dominated the country since the US-led invasion of 2003 toppled Saddam Hussein.

Many of Iraq's longtime political figures -- seemingly irremovable since the dictator's fall -- were pushed out of their seats by new faces.

The supreme court, whose rulings are final, also ratified parliament's decision to dismiss Iraq's nine-member electoral commission and have them replaced by judges.

The United Nations said it was ready to help and advise electoral authorities and called on all sides to respect the law and resolve their differences peacefully.

UN Iraq envoy Jan Kubis said in a statement he was "confident" authorities would find ways to recount the vote quickly and "in a fully transparent way, that will increase public confidence in the election process".

The recount is unlikely to produce a major change in the number of seats won by rival lists, according to experts, but rather modify the rankings of candidates within the same lists.

"The major blocs could win or lose three seats," said judicial expert Haidar al-Soufi.

- 'No constitutional vacuum' -

Tarek al-Marmouri, another expert, said even if a manual recount takes weeks "there will be a legislative but no constitutional vacuum" because Prime Minister Haider al-Abadi's government would stay on in a caretaker capacity.

When Sadr's bloc scooped the most seats in May's election it was seen as a blow for Tehran, long the dominant foreign player in conflict-hit Iraq.

The Shiite firebrand had railed against both the influence of Iran and the United States, even drawing closer to Tehran's arch-foe Saudi Arabia.

But on June 13, he announced an alliance with pro-Iranian Hadi al-Ameri, head of a rival list made up of former members of the mainly Shiite paramilitary units which defeated the IS jihadists.

It is in the multi-ethnic, oil-rich northern province of Kirkuk that the challenge to the election results has been the strongest -- and the most potentially explosive.

Kirkuk's population -- majority Kurdish but with sizeable Arab and Turkmen minorities -- pushed Iraqi authorities to impose a curfew on the night of the results.