Iraqi forces are ahead of schedule as they advance in the battle to retake Mosul from the terrorist group Islamic State.

In a presser at Washington, U.S. spokesperson Peter Cook said, "Early indications are that Iraqi forces have met their objectives so far, and that they are ahead of schedule for this first day."

But he warned that the campaign would be a "difficult fight" and "could take some time" as it remained to be seen how the jihadists respond to the strike.

A coalition of about 30,000 Iraqi forces, Kurdish fighters, Sunni Arab tribesman and Shia forces with support from the US military formed parts of the battle to take control of the jihadists' last stronghold in Iraq.

Forces advanced at night time and took control of most villages in the first few hours of the operation. They were also able to secure an additional stretch of road from Kurdish city Irbil to Mosul.

It has also been reported that the forces are yet to retake around 70 villages before they reach to the outskirts of the town.

As the fighting gets closer, concerns are been raised over the safety of the civilians trapped in the area.

Reports from AFP stated that the civilian are happy. Hazem Diedio Cardomi, a civilian in Irbil, said that he had gone through a lot of suffering and now they look forward to returning to their region soon.

Reports from BBC stated that people have a mix feeling of happiness and fear about how IS would treat them and the danger of being caught in air strikes or crossfire.

Cook has said that as many of seven million leaflets have been dropped over Mosul explaining to residents "the safest way to conduct themselves as this fighting plays out".

IS militants took control of Mosul in June 2014 and their leader, Abu Bakr al-Baghdadi chose a mosque to proclaim the establishment of a "caliphate" and taking over Mosul would be significant.