Iraqi forces backed by jets, drones and gunships attacked Mosul airport on Thursday in a key step in their four-month-old offensive to retake the city from the Islamic State group.
The disused airport commands access to the south of the city, which the jihadists seized in June 2014 and where their leader Abu Bakr al-Baghdadi proclaimed a "caliphate" straddling Iraq and Syria in 2014.
Federal police and the interior ministry's Rapid Response units reached the walls of the airport compound, which lies on the west bank of the Tigris River that runs through the city, AFP correspondents reported.
"Right now we're on the southern edge of Mosul airport and the sugar factory, our troops are attacking it," said Hisham Abdul Kadhem, commander of the Rapid Response's Scorpion Regiment.
He said his forces and federal police controlled the southern and western sides of the airport.
"Engineers are starting to clear the roads and remove IEDs (improvised explosive devices)," he said, as an attack helicopter fired rockets at the sugar factory.
There was no sign that government forces had entered the airport yet but the regional command coordinating the battle said elite Counter-Terrorism Service forces also attacked the neighbouring Ghazlani military base, where some of them were stationed before IS seized the city in June 2014.
Control of the base and airport would set government forces up to enter Mosul neighbourhoods on the west bank of the Tigris, a month after declaring full control of the east bank.
All of the city's bridges across the river have been blown up.
The US-led coalition has played a key role in supporting Iraqi forces with air strikes and advisers on the ground, and on Thursday US forces in armoured vehicles were seen moving on the airport.
The American troops are not supposed to be doing the actual fighting but in recent weeks have got so close to the front that they have come under attack, coalition spokesman Colonel John Dorrian said.
"They have come under fire at different times, they have returned fire at different times, in and around Mosul," Dorrian told reporters on Wednesday.
He declined to say if there had been any US casualties in the attacks, but an unnamed official later told CNN that several personnel had been evacuated from the battlefield.
The latest push to retake Mosul, the second city and the last stronghold of the jihadists in Iraq, was launched on Sunday and involves thousands of security personnel.
They started closing in on the airport four days ago. It is unclear how many jihadists are defending the airport but US officials said Monday that only around 2,000 remain in Mosul.
There are an estimated 750,000 civilians trapped on the city's west bank, which is a bit smaller than the east side but more densely populated.
It is home to the Old City and its narrow streets, which will make for a difficult terrain when Iraqi forces reach it because they will be impassable for some military vehicles.
The noose has for months now been tightening around Mosul and the living conditions for civilians are fast deteriorating.
Residents AFP has reached by phone spoke of dwindling food supplies forcing many families to survive on just one meal a day.
Medical workers say the weakest are beginning to die of the combined effect of malnutrition and the lack of medicines, which IS fighters are keeping for themselves.
A smaller than expected proportion of the east side's population fled when Iraqi forces stormed it nearly four months ago but the United Nations is bracing for a bigger exodus from the west.
It had said 250,000 people or more could flee their homes on the west bank and has scrambled to set up new displacement camps around the city.