The battle to retake the Iraqi city of Mosul from Isis has begun, Iraq's Prime Minister, Haider al-Abadi, has said.
Mosul, which is regarded as Isis' "second city", is the last major stronghold of the jihadist group in Iraq.
It has been under the group's control since June 2014, but the Iraqi offensive to retake the city has been planned for months.
In an address on state television, Mr 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, using another term for the jihadist group.
US and French forces had already begun bombing Isis targets in Mosul ahead of the offensive.
Isis fighters are said to be dug in and preparing to battle hard to maintain control, Reuters reported.
Ahead of the battle, the Iraqi army dropped tens of thousands of leaflets over Mosul urging residents to hide before the offensive begins.
The leaflets carried several messages to the citizens of the city in northern Iraq attempting to reassure them that the advancing army "would not target civilians" but warned them to avoid the known locations of Isis militants.
"Keep calm and tell your children that it is only a game or thunder before the rain," a leaflet said. "Women should not scream or shout, to preserve the children's spirit."
"If you see an army unit, stay at least 25 metres away and avoid any sudden movements," another said.
They have previously forced civilians to remain where they are rather than flee during previous battles to maintain territory.
The offensive to "liberate" Mosul from ISIS has begun. CNN’s Arwa Damon is near Mosul and describes what she's seeing pic.twitter.com/3Zskk5WzGI— CNN (@CNN) October 17, 2016
It comes just hours after they lost control of the symbolically important town of Dabiq in Syria to a group of rebels after a short battle.
The opposition fighters were able to retake the town with "minimal" resistance despite Isis prophecies that Dabiq was to be the scene of an apocalyptic final battle between Muslims and Christians.
Isis has lost a third of its territory in Iraq and Syria in the past year as counter insurgent forces and air strikes push the group back.
Last week, the UN warned that it was bracing itself for the world's biggest and most complex humanitarian effort following the battle which it expects to displace up to one million people and see civilians used as human shields or even gassed.
Camps have been prepared on the outskirts of Isis territory to cope with the movement of people.
The Iraqi government launched a radio station to help Mosul residents stay safe during the offensive last month broadcasting from Qayyara, a town around 40 miles south of the city.
On Sunday, the Iraqi Prime Minister Haider al-Abadi confirmed that Shia militants would not enter the heavily Sunni city.
Previously local Sunni politicians and regional Sunni-majority states including Turkey and Saudi Arabia had warned that Shia soldiers taking part could lead to sectarian fighting.