A boy rides his bike past destroyed cars and houses in a neighborhood recently liberated by Iraqi security forces, on the western side of Mosul, Iraq on Sunday, March 19, 2017.

The battle for western Mosul looks to be the most devastating yet for Iraqi civilians trapped between advancing troops and Islamic State militants.

The UN estimates that 400,000 Iraqi civilians are trapped in the Old City of Mosul as government forces try to capture it from Islamic State militants.

Middle East Editor Jeremy Bowen, producer Pete Emmerson and cameraman Nik Millard have been to the edge of the old city.