According to a US general, between 800 and 900 ISIS group fighters have been killed since Iraqi government launched a comprehensive operation to recapture Mosul from the militants.

“Just in the operations over the last week and a half associated with Mosul, we estimate they've probably killed about 800-900 Islamic State fighters,” General Joseph Votel, who heads the US military's Central Command, said during an interview with AFP.

The operation, which aims to push ISIS terrorists out of Mosul and its surroundings, began days ago and has been successful in freeing numerous villages and regions from the militant group.

According to earlier US estimates, the population of ISIS fighters in Mosul city was between 3,500 and 5,000, and up to 2,000 others were thought be in the broader Mosul region.

Votel, however, said that it was hard to provide exact numbers since ISIS fighters move around the city and are among the local population.

Recent advances on the eastern front have brought elite Iraqi forces to within 5km of Mosul.

Residents told AFP that the militants seemed to be preparing for an attack on the city itself.

This is while tens of thousands of Iraqi fighters have been advancing on Mosul from the south, east and north after an attack was launched on 17 October to retake Mosul.