MOSUL - Iraqi forces backed by helicopter strikes engaged in heavy fighting with jihadists on the outskirts of the Old City on Sunday as they pressed an offensive to recapture west Mosul . The elite Rapid Response Force and Iraqi federal police attacked the Islamic State group militants with rifles, machineguns, mortar rounds and rockets a month after the west Mosul operation began.

The joint forces were around 100 metres (yards) south of Mosul 's Iron Bridge, which has been destroyed along with other bridges that span the Tigris River that linked the city 's eastern and western sides. Helicopters circled overhead harrying IS with barrages of bullets and rocket fire in strikes aided by weather that was clearer than it had been in recent days, AFP correspondents said. "The aim of the battle is to go past Al-Hadidi (Iron) Bridge northwards," Brigadier General Abbas al-Juburi of the Rapid Response units told AFP.

He said the operation was complicated by the presence of hundreds of thousands of civilians believed to have stayed on under jihadists rule.

"The difficulties are the presence of families, how to avoid opening fire on families who are used as human shields" by IS jihadists, Juburi said. The battle for the densely populated Old City , with its warrens of alleyways, was always expected to be the toughest of the campaign to retake Mosul from IS. In January Iraqi forces retook the east side of the city before setting their sights on the west.