In 2012, the sunni minority in power under Saddam Hussein, but marginalised after the us intervention, had led a protest campaign against the government, controlled by the shiites, accused of wanting to monopolize all powers.
The objective of the iraqi troops is to take Anna, and then Rawa and finally Qaïm, last town before the border and the province of syria, Deir ez-zor.
Located west of the ethnically divided Kurdish-held city of Kirkuk, Hawija also lies on a fault line of Arab-Kurdish tensions.
"We announce the launch of the first phase of the liberation of Hawija, in fulfilment of our pledge to our people to liberate all Iraqi territory and to cleanse it from the terrorist Daesh gangs", Abadi said, using the Arabic acronym for ISIL.
Hours into Thursday's offensive, Iraq said its forces had gained ground against Islamic State.
But it was surrounded and cut off from other IS-held territory more than a year ago, when government forces advanced north towards the second city of Mosul.
Iraqi Federal Police will be deployed to Shirqat, while Counter-Terrorism Service and the Rapid Response Forces will fight ISIS in Hawija.
"They have already suffered horribly under ISIS rule.food, water and medicine are running out, with many children reportedly weak and malnourished", the organisation said.
"Now families face a bad choice of staying put as fighting intensifies, or risking their lives to flee on foot for up to 12 hours through minefields and snipers, then wade across a river to reach safety".
The report also showed how ISIS fighters used civilians as human shields, forcing them from neighbouring villages into battle zones in west Mosul, while also trapping them in their homes to prevent them from escaping.
The offensive on Hawija should not affect the Kurdish plan to hold the referendum in Kirkuk on Monday, a Kurdish official told Reuters.