Iraqi special forces have begun a major military build up outside Mosul ahead of a planned offensive to retake the ISIL held city.

The operation to retake Mosul is expected to be the most complex yet for Iraq’s army and comes as the US-led coalition increases air strikes against militants in and around the city.

In a statement, the coalition said its planes had conducted more than 50 airstrikes against the so-called Islamic State group in the area over the past two weeks.

“We arrived here at 4am during sunrise. We have come to liberate Mosul. We will liberate it and we will make sure the families can return home,’‘ said one Iraqi army spokesman.

Mosul has been under ISIL control for more than two years. Around 30,000 Iraqi and coalition forces are expected to take part in the offensive, which the United Nations fears could spark a major humanitarian emergency.

Lise Grande, UN Humanitarian Coordinator for Iraq said:
“The U.N. estimates that in a worst case scenario, Mosul could represent the single largest most complex humanitarian operation in the world in 2016. There are a number of reasons why it is so complex. The sheer scope of the expected operation, in a worst case scenario there could be 1.2 to 1.5 million civilians inside of the city who could be impacted.”

Potentially the biggest battle in Iraq since the US-led invasion in 2003, the assault for Mosul is predicted to begin by the end of this month.