The involvement of the Iranian-backed Shia militias has raised concern that the battle for Mosul, a Sunni-majority city could aggravate sectarian tensions.The militias say they will not enter the city itself. Jaafar al-Husseini,a spokesman for the Hezbollah Brigades,said his group and the other militias were advancing with the aid of Iranian advisers and Iraqi aircraft.He said the US-led coalition is not playing any role in the Shia militias' advance