A firebrand cleric who led a militia which fought British and American troops in Iraq is on course to win the country’s elections, in what would be a surprise upset for Western-backed incumbent Haider al-Abadi.

Moqtada al-Sadr’s Sairoon alliance of reformed Shia militants and communists was ahead in eight of Iraq's 18 provinces and second in four others.

His Mahdi Army waged a brutal and costly insurgency against coalition troops during the 2006-2008 civil war and offered a reward for any British soldiers captured.

Mr Sadr has since disavowed violence against fellow Iraqis and in 2008 ordered his forces to become a humanitarian group.

Mr Sadr himself rebranded as a secular nationalist, campaigning against corruption and for reform, a message which seemed to resonate with Iraqis tired of entrenched sectarianism and graft.