KHAZIR, Iraq (AP) — The US-led coalition is increasing airstrikes in and around the militant-held city of Mosul as Iraqi ground forces build up ahead of a planned operation to retake the city, it said in a statement Friday.

The coalition said its planes had conducted more than 50 airstrikes against the Islamic State group in the Mosul area over the past two weeks.

"We have been intensifying our efforts in and around Mosul," said Col. John Dorrian, a spokesman for the US-led coalition.

Iraqi ground forces are moving into place to the south and east of Mosul. While Qayara air base to the south of Mosul remains the main base of operations, Iraqi army convoys, including a unit of the country's elite special forces, could be seen traveling to frontline positions to the east of the city.

"All the troop movements now are related to the Mosul operation," said Iraqi Army Brig. Gen. Firas Bashar, stationed at an Iraqi army base in Makhmour.

The operation to retake Mosul is expected to be the most complex yet for Iraq's military. Iraqi and coalition forces say some 30,000 troops will be needed to retake the city that has been under IS control for more than two years.