Iraqi forces members, consisting of the Iraqi federal police and the elite Rapid Response Division, patrol in the Shifa neighbourhood, on the west bank of Mosul, on June 17, 2017, where they are battling some of the last members of the Islamic State (IS) jihadist group in the city. (Xinhua/AFP Photo)

MOSUL, Iraq, June 18 (Xinhua) -- Iraqi government forces started on Sunday a major operation to enter the last Islamic State (IS) stronghold of the old city center in western Mosul, the Iraqi military said.

The regular army, Counter-Terrorism Forces and the Federal Police started decisive battles against the extremist IS militants in Mosul's old city center, Abdul-Amir Yarallah from the Joint Operations Command (JOC) said in a brief statement.

The troops started their push into the old city at 6:00 a.m. local time (0300 GMT) from three directions, Yarallah said, adding that the results of the new push will be announced later.

Three days ago, the Iraqi soldiers freed the small neighborhood of Bab Sinjar at the entrance of the old city, putting the troops on new positions at the edge of adjacent al-Farouq area at the major IS redoubt in the old city center, Yarallah said on Thursday.

Iraqi forces, backed by international coalition, are fighting to drive out IS militants from the western side of Mosul, locally known as the right bank of Tigris River, but al-Shifaa neighborhood and most of the densely-populated old city center, are still under control of the extremist militants.

According to the Iraqi military, more than 95 percent of the city has been retaken from IS in the ongoing major offensive launched in October last year.

Mosul, 400 km north of Iraq's capital Baghdad, has been under IS control since June 2014, when government forces abandoned their weapons and fled, enabling IS militants to take control of parts of Iraq's northern and western regions.