KHAZER, Iraq — Islamic State militants have deployed suicide car bombs and fired mortar rounds to slow down the advance of Iraqi troops outside a key town near the militant-held city of Mosul.

An officer with the Iraqi army's 9th Division told The Associated Press on Wednesday that his troops are around 1 kilometer (half mile) away from Hamdaniyah, a historically Christian town also known as Bakhdida.

He says IS has sent 12 car bombs since Tuesday, all of which were blown up before reaching their targets. He says troops suffered a small number of casualties from the mortar rounds, without providing figures.

The officer spoke on condition of anonymity because he wasn't authorized to talk to reporters.

Iraq launched a massive operation on Monday to retake Mosul, the country's second largest city.