Iraqi security forces have entered the site of the destroyed Great Mosque of al-Nuri in Mosul after driving back militants from Islamic State. BBC Correspondent who is embedded with troops there, says the complex has not yet been secured and is exposed to IS sniper and mortar fire.<br/><br/>Militants blew up the medieval mosque and its landmark leaning minaret last week as troops advanced towards it. But the site is still of great symbolic importance to both sides in the battle. IS is now in retreat across Iraq and neighbouring Syria, where a US-backed alliance of Kurdish and Arab fighters is laying siege to its de facto capital of Raqqa. <br/><br/>Pro-government forces launched an offensive to retake Mosul in October with air and ground support from a US-led multinational coalition. They managed to take full control of the eastern half of Mosul in January and started an assault on the west the following month.