Iraqi Prime Minister Haider al Abadi says the operation which began Monday will liberate the city from "the violence and terrorism of Daesh".
An offensive to retake the Iraqi city of Mosul from Daesh began in the early hours of Monday, Iraqi Prime Minister Haider al Abadi announced on state television. The UN refugee agency, UNHCR, says the assault may cause a large number of Iraqis to seek refuge in neighbouring countries.
Iraqi government troops along with the US military, local militias and Kurdish Peshmerga forces launched an operation to rid Mosul of Daesh. Turkey, which has a presence in Bashiqa, 19 kilometres from Mosul, and in Zilkan, will also be part of the offensive.
Iraq's second-largest city has been under Daesh control since 2014 and the outcome of this battle will be decisive for the future of the country.
"UNHCR is concerned that events in Mosul may cause up to 100,000 Iraqis to flee towards Syria and Turkey," the body said. "Preparedness plans are underway in Syria to receive up to 90,000 Iraqi refugees."
Around half of some 3,000 Iraqi forces trained by Turkey at the Bashiqa camp in northern Iraq are taking part in the operation to drive Daesh from the city of Mosul, Turkish military sources said on Monday. One of the sources said there were Shias, Yazidis, Turkmens and Christians in the force.
In his address broadcast by Iraqiya channel earlier in the day, Abadi said "the time of victory has come and operations to liberate Mosul have started."
"Today I declare the start of these victorious operations to free you from the violence and terrorism of Daesh," he said, addressing residents of the Mosul region.
The prime minister added that only the army and police will enter Mosul.
"The force leading liberation operations is the brave Iraqi army with the national police and they are the ones that will enter Mosul, not others," he said on state television.
BREAKING: the Iraqi-led offensive to retake ISIL-held Mosul has begun. It may take months to clear it of 3,500-5,000 ISIL fighters— Ali Velshi (@AliVelshi) October 16, 2016
Airstrikes pounding in the distance, soldiers catching last couple of hours of sleep in their humvees here before rolling out for Mosul op— Mike Giglio (@mike_giglio) October 16, 2016
Peshmerga forces are reportedly deployed on the Khazir front some 40 kilometres east of Mosul. US artillery units also began striking Daesh positions on different fronts.
The primary targets of the offensive are the Hamdaniya and Karakus districts.
Peshmerga commander Colonel Seyit Khajar said approximately 18,000 fighters are participating in the offensive on several fronts in eastern and southeastern Mosul.
In Washington, US Secretary of Defense Ash Carter described the launch as a "decisive moment" to completely defeat Daesh and said Washington has confidence in its Iraqi partners to free Mosul and the rest of Iraq from the terror group.
"The United States and the rest of the international coalition stand ready to support Iraqi Security Forces, Peshmerga fighters and the people of Iraq in the difficult fight ahead," Carter said in a statement.
In the build up to the full-scale offensive, the US military began shelling Daesh targets early on Sunday morning.
Iraqi federal and allied forces have been tightening the noose on Mosul for months.
They recently retook key positions around Qayyarah, a town some 60 kilometres south of Mosul, setting the stage for a final push on Daesh's northern bastion.
Not long after the launch of the Mosul military operation, a suicide bombing killed 10 people and wounded 25 at a security checkpoint south of Baghdad. Daesh has intensified bomb attacks in government-held areas this year as it loses territory to US-backed Iraqi government forces and Shia militias.
Earlier on in the day, Turkish-backed FSA rebels recaptured Syria's Dabiq from Daesh.