REPUBLIKA.CO.ID, TIKRIT -- Iraq said security and allied forces backed by US-led coalition aircraft "liberated" the city of Tikrit on Tuesday, its biggest victory yet in the fight against Islamic State jihadists.

The operation to retake the hometown of former president Saddam Hussein began on March 2 and had looked bogged down before Iraqi forces made rapid advances in the past 48 hours.

Prime Minister Haider al-Abadi "announces the liberation of Tikrit and congratulates Iraqi security forces and popular volunteers on the historic milestone," his official Twitter account said.

He was referring to paramilitary groups which played a major role in the fighting to retake Tikrit, a Sunni Arab city which IS had controlled since it captured swathes of Iraq in June.

A spokesperson for the US-led coalition told AFP however that "parts of the city remain under (IS's) control and there is still work to be done."

In a statement to AFP just minutes before Abadi's tweet, his spokesman Rafid Jaboori said: "Iraqi forces reached the centre of Tikrit, raised the Iraqi flag and are now clearing the city."

The provincial government headquarters was retaken on Monday and on Tuesday the Iraqi tricolour replaced the black IS flag on the building.

In scenes captured in an AFP video, jubilant fighters can be seen tearing up the black flag amid the extensive destruction in the city.

"We are in the centre of Tikrit. The city and all administrative buildings were completely liberated," said one of them, policeman Bahaa Abdullah Nasif.

Iraqi military officials have been saying since the start of the operation that IS fighters had laid thousands of bombs in streets, houses and tunnels to make their last stand.

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