Iraqi forces have opened a front near Mosul in preparation for a future assault on the city, which is held by Islamist State (IS) extremists.
Security officials said elite counterterrorism forces and two army divisions advanced on June 18 from the northern refinery town of Baiji towards an airfield near Qayara, which they hope to take and use as a staging ground to retake Mosul.
Mosul is Iraq's largest northern city and the Islamic State group's de facto capital in the country.
The advance comes as, farther west, Iraqi forces entered the center of Fallujah earlier on June 18.
The capture of the city center follows a four-week operation to retake Fallujah from IS fighters who had controlled it since mid-2014.
