Iraq election: Nationalist cleric Muqtada al-Sadr on course to beat prime minister

Nationalist Shia cleric Muqtada al-Sadr is on course to win the Iraqi election.

Powerful nationalist Sadr was leading in the polls with more than half the votes counted, the electoral commission said, a surprise comeback for a Shia leader who had been sidelined by Iran-backed rivals.

The partial results are a severe blow to incumbent Prime Minister Haider al-Abadi, whose Victory Alliance party is currently third in the polls, according to partial results, with Shia militia chief Hadi al-Amiri's bloc, which is backed by Tehran, in second place.

Sadr, the former leader of the anti-Western Mahdi Army during the US occupation, ran on a campaign promising to stamp out corruption.

Forming an unexpected alliance of his Islamist Sadrist Movement party with six mainly secular parties including the communist party, the Saairun ["Marching forwards"] alliance has widened its support base to include much of Iraq's youth and poor.

From the archives: The moderation of Muqtada al-Sadr

Sadr also gained popularity commanding Shia paramilitary groups in the fight against the Islamic State group which overran large swathes of Iraq in 2014.

Abadi, who entered Saturday's election as a frontrunner, was hoping to consolidate support over the defeat of the extremist group, announced in December last year.

Unlike Abadi, a rare ally of both the United States and Iran, Sadr is an enemy of both countries that have wielded influence in Iraq after the US-led invasion that toppled Sunni dictator Saddam Hussein and ushered the Shia majority to power.

Sadr has led two uprisings against US forces in Iraq and is one of the few Shia leaders to distance himself from Iran.

In September last year, Sadr made a surprise state visit to Iran's Sunni rival Saudi Arabia.

Sadr's apparent victory does not mean his bloc could necessarily form the next government. Overall, just under 7,000 candidates are standing and Iraq's complex system means no single bloc is likely to get anything near a majority in the 329-seat parliament.

Whoever wins the most seats must negotiate a coalition government, expected to be formed within 90 days of the official results, due later on Monday.

Turnout in the ballot was 44.5 percent, much lower than previous elections.