Iraqi Prime Minister Haider al-Abadi planted the national flag in Ramadi after the army recaptured the city centre from IS.

'Over the past month, we've killed 10 ISIL leadership figures with targeted air strikes, including several external attack planners, some of whom are linked to the Paris attacks,' said US Army Colonel Steve Warren, a spokesman for the US-led campaign against the Islamist group also known by the acronym ISIL.

One of those killed was Abdul Qader Hakim, who encouraged the militants' outside operations, Warren said. He was killed in the northern Iraqi city of Mosul on December 26. Two days prior, a coalition air strike in Syria killed Charaffe al Mouadan, a Syria-based IS member with an direct connection to Abdelhamid Abaaoud, the associated ringleader with the planned bombings and shootings in Paris on November 13 which killed 130 individuals, Warren added.

Air strikes on IS's leadership clarified recent battlefield triumphs against the group, which additionally lost control of a dam on a vital supply route close to its true capital of Raqqa in Syria on Saturday. 'Part of those successes is attributable to the fact that the organisation is losing its leadership,' Warren said. He warned, however: 'It's still got fangs.'

The Iraqi armed force's seisure of the centre of Ramadi on Sunday is its first significant victory against the hardline Sunni Islamists that cleared through a third of Iraq in 2014, and came after quite a while of cautious advances backed by coalition air strikes. Ramadi was the main city to have fallen under IS control since Abadi took office in September 2014.

The retaking of Ramadi recommended Abadi's system of substantial US air support while sidelining the Shi'ite volunteer armies could be effective. The militias have served as a defense against IS but drawn protests from Washington. Coalition representative Warren said casualties to Iraqi forces during the fight for Ramadi were in the low double digits. He and Iraqi authorities put IS casualties in the hundreds.

The government has selected the mostly Sunni city of Mosul, 400km north of Baghdad, as the next target for Iraq's armed forces.