BAGHDAD - Iraq brought all of its territory still held by the Islamic State group under attack Thursday, throwing the jihadists on the defensive across their self-proclaimed "caliphate" extending into neighbouring Syria.
Security forces backed by paramilitary units launched a dawn assault on a besieged IS-held pocket around the northern town of Hawija, just days after attacking the jihadists' only other foothold in the country.
The territory still held by IS has been dwindling fast since its defeat in Iraq's second city Mosul in July, with stronghold after stronghold coming under assault on both sides of the border with Syria.
Most of its onetime Syria bastion Raqa, long a byword for its most gruesome atrocities, is now in the hands of US-backed fighters, while elsewhere in Syria IS has suffered major losses to Russian-backed government forces.
Iraqi Prime Minister Haider al-Abadi predicted that the assault on the Hawija region would swiftly bring a new victory against the crumbling jihadists.
The mainly Sunni Arab enclave, which was bypassed by government forces in their advance north to Mosul last year, has been a bastion of insurgency ever since the first year of the US-led occupation in 2003.
After the defeat of IS in Mosul and the recapture of adjacent areas, Hawija and neighbouring towns form the last enclave still held by IS in Iraq apart from a section of the Euphrates Valley downstream from the border with Syria.
- 'Victory after victory' -
"At the dawn of a new day, we announce the launch of the first stage of the liberation of Hawija, in accordance with our commitment to our people to liberate all Iraqi territory and eradicate Daesh's terrorist groups," Abadi said, using an Arabic acronym for IS.
"Greetings to all of our forces, who are waging several battles of liberation at the same time and who are winning victory after victory and this will be another, with the help of God," he said.
One correspondent heard heavy shelling around the IS-held town of Sharqat where Iraqi forces have been massing in recent days.
A spokesman for Iraq's Joint Operations Command, General Yahya Rasool, said retaking Sharqat was the first goal of the offensive.
The US-led coalition fighting IS hailed the new offensive by the Iraqi security forces against the jihadist group, also known as ISIS.
"Daesh is losing ground and failing in every battle. Soon ISIS will have no sanctuary in Iraq," said coalition spokesman Colonel Ryan Dillon.
- Concern for civilians -
Humanitarian organisations expressed concern for the fate of civilians caught up in the offensive.
"The 85,000 civilians still in and around Hawija, including around 40,000 children, now face a terrifying time as they worry about getting caught up in the fighting or being hit by an air strike," said International Rescue Committee acting country director Jason Kajer.
"For those who decide to flee, there is a significant risk of being targeted by ISIS snipers or killed by a mine."
The Hawija area was the second after Mosul to be captured by IS in its lightning offensive through the Sunni Arab heartland north and west of Baghdad in 2014.
Its inhabitants are deeply hostile both to the Shiite-led government in Baghdad and to the Kurds who hold adjacent areas of Kirkuk province where they form the historical majority.
Preparations for the offensive against Hawija have been overshadowed by an independence referendum that Kurdish leaders plan to hold on Monday, in areas including Kirkuk, against the wishes of the federal government in Baghdad.
IS has seen the territory under its control fast diminish in recent months in the face of multiple offensives against its fighters in both Iraq and Syria.
On Tuesday, Iraqi forces launched an attack up the Euphrates Valley against the other one of IS's two remaining enclaves in Iraq.
And in Syria's eastern province of Deir Ezzor, IS faces twin assaults -- one by Russian-backed government troops and the other by US-backed fighters of the Syrian Democratic Forces.
Further up the Euphrates, the SDF now controls 90 percent of the city of Raqa, the Britain-based Syrian Observatory for Human Rights war monitor said on Wednesday.
The US-led coalition supporting the SDF estimated that 65-70 percent of Raqa is now under the control of the alliance of Kurdish and Arab fighters.
The jihadists seized Raqa in early 2014, making it their de facto Syria capital. They are thought to have used the city to plan attacks abroad.
IS also holds pockets of territory elsewhere in Syria, notably in eastern parts of the central provinces of Homs and Hama, but it has come under attack by Russian-backed government forces there too.