Mission Accomplished: Abadi declares 'end of war against IS' in Iraq

Iraqi Prime Minister Haider al-Abadi on Saturday declared victory in a three-year war by Iraqi forces to defeat the Islamic State militant group, which at its height endangered Iraq's very existence as a country.

"Our forces are in complete control of the Iraqi-Syrian border and I therefore announce the end of the war against Daesh (IS)," Abadi told a conference in Baghdad.

"Our enemy wanted to kill our civilisation, but we have won through our unity and our determination. We have triumphed in little time," he said.

The defeat of the Islamic State group is a massive turnaround for an organisation that in 2014 ruled over seven million people in a territory as large as Italy encompassing large parts of Syria and nearly a third of Iraq.

IS seized vast areas north and west of Baghdad in a lightning offensive in 2014.

As Iraq's army and police retreated in disarray at the time, Ayatollah Ali Sistani - spiritual leader of the country's majority Shia population - called for a general mobilisation, leading to the formation of Hashd al-Shaabi paramilitary units.

Iraq's fight-back was also launched with the backing of an air campaign waged by a US-led coalition, recapturing town after town from the clutches of the militants in fierce urban warfare.

Last month, Iraqi forces and local tribal fighters captured Rawah, the last town in the country held by the Islamic State group, leaving just a slither of territory in the militants' hands.

Iraq's close ally Iran already declared victory over IS last month, as the group clung to just a few remaining scraps of territory.

But Abadi said at the time that he would not follow suit until the desert on the border with Syria had been cleared. 

"I announce the good news: the liberation by Iraqi forces of the whole of the Iraqi-Syrian border," the prime minister told the conference organised by the Iraqi journalists' union.

The head of Iraq's Joint Operations Command set up to fight IS, General Abdel Amir Yarallah, gave an update on Saturday to announce that the desert valley of al-Jazira was under the control of Iraqi troops and the Hashd al-Shaabi all the way from Nineveh province in the north to Anbar in the west.

Federal forces "now control the border with Syria from al-Walid border crossing to that of Rabia", covering a distance of 435 kilometres, he said.

In Syria, IS have faced separate onslaughts by forces backed by Russia and the US in Deir az-Zour province and now control just a tiny sliver of the region along the Euphrates river.

On Thursday, Russia's defence ministry said its mission in support of the Syrian regime to oust IS militants had been "accomplished" and the country was "completely liberated".

In the border region, pro-regime forces and US-backed Kurdish-led forces are conducting operations to clear IS fighters from the countryside north of the Euphrates valley after ousting them from all Syrian towns.

Despite the victory announcements, experts have warned that IS retains the capacity as an insurgency group to carry out high-casualty bomb attacks through sleeper cells.

It also retains natural hideouts in the deep gorges of Wadi Hauran, Iraq's longest valley stretching from the Saudi border up to the Euphrates River and the frontiers with Syria and Jordan.