The UN deputy Secretary General for Humanitarian Affairs and Emergency Relief voiced grave concern at risks faced by civilians as operations to retake the Iraqi city of Mosul began.<br/><br/>Stephen O'Brien said that the UN is 'extremely concerned' for 1.5 million civilians in Mosul who may be affected by military operations to retake the city from ISIL. With the support of Iran and a US-led coalition, Iraqi forces have since regained much of the ground lost to IS.<br/><br/>Meanwhile US Secretary of Defence Ash Carter has said that operations to retake the Iraqi city of Mosul from the Islamic State group is a decisive moment in the campaign to deliver ISIL a lasting defeat. Carter promised continued support for Iraq.<br/><br/>He emphasised that the United States and the rest of the international coalition stand ready to support Iraqi Security Forces, Peshmerga fighters and the people of Iraq in the difficult fight ahead.<br/><br/>The northern city was where IS supremo Abu Bakr al-Baghdadi publicly proclaimed a "caliphate" straddling Iraq and Syria in June 2014.