US-backed Iraqi forces pushed deeper into western Mosul today after retaking the city's airport from Islamic State and punching into built-up areas of the terrorists' last major stronghold in the country. <br/><br/>Troops advanced in several more populated, built-up southern districts and about 1,000 civilians walked across the frontlines. It is the largest displacement of civilians since fighting began a week ago in a bid to deal Islamic State a decisive blow.<br/><br/>The advancing forces are now less than three kilometers from the mosque in Mosul's old city where Islamic State leader Abu Bakr al-Baghdadi declared a caliphate in 2014.