Peshmerga forces advance in the east of Mosul to attack Islamic State militants in Mosul, Iraq, October 17, 2016. [Photo/Agencies]

BAGHDAD -- Iraqi forces are fighting all out to retake control of the city of Mosul from the Islamic State (IS) militants after Iraqi Prime Minister Haider al-Abadi on Monday announced the start of long-awaited offensive.

"Today I declare the launch of the operation of liberating Nineveh province. The time of victory has come, and the moment of the great victory is approaching," Abadi said in his brief address aired by the state-run al-Iraqiya channel.

Abadi pledged to rebuild Mosul and other towns and villages in Nineveh province after they were destroyed by the extremist IS militants, and vowed to bring stability to Mosul.

"Very soon, we will be with you to raise the flag of Iraq in the middle of Mosul, and in towns and villages as well," Abadi said, calling on the people of Mosul to cooperate with security forces to defeat the IS group.

Like the previous battles that freed the cities of Tikrit, Ramadi, Fallujah and others from IS militants, the troops are moving to gradually encircle the city of Mosul, some 400 km north of the Iraqi capital of Baghdad, after clearing IS militants from towns and villages around it, before entering the city districts.

On Monday morning, the Iraqi forces reportedly managed to free nine villages from IS militants who fled the scene, as they continued their advance to free many areas around Mosul, including the towns of Bashiqa and Himdaniyah in northeast of the city.

In Mosul, reports said that some 1.3 million civilians are still living in Mosul's neighborhood and surrounding villages of Nineveh plain, while more than 5,000 IS militants holed up in the city with significant preparations to defend the city.

"More than 65,000 Iraq security personnel are expected to participate in the battle of Mosul, their positions located between 15 to 50 km away from the edges of the city's neighborhoods," Major Abdullah al-Jubouri, an Iraqi army officer, told Xinhua.

Army brigades backed by elite anti-terrorism forces with an armored brigade, including Abrams tanks, are advancing from the southern axis on the eastern side of the Tigris River. Other army brigades and anti-terrorism forces are also advancing from southeastern axis on the west side of the river, Jubouri pointed out.

There are also some 10,000 fighters of the Kurdish Peshmerga fighters who are advancing from the east and northern axis. The Kurdish forces are backed by some 24,000 of police of Nineveh province and paramilitary Sunni tribal units, Jubouri said.

The Iraqi forces in Mosul battle are also supported by the Iraqi and international aircraft as well as different kinds of Iraqi and U.S.-led coalition artillery units, Jubouri added.

Observers believe that the battles in Mosul could be long, bloody, costly and protracted, let alone the suffering of civilians, but that will mainly depends on whether the IS militants would be ready to show stiff resistance or not.