Iraqi forces on Friday entered a west Mosul neighbourhood for the first time since the October launch of a massive offensive to retake the city from the Islamic State (IS) militant group.
The push on Al-Maamun, a small neighbourhood on the southwestern edge of Mosul, came after government troops retook the airport, which commands access to the city from the south, and a nearby military base.
The IS militants have been on the back foot in both Iraq and neighbouring Syria, the twin pivots of the "caliphate" they declared in July 2014.
Turkish-backed rebels ousted IS from the strategic Syrian town of Al-Bab on Thursday, although they suffered twin reverses on Friday with suicide bombers killing 42 people just outside the town and two Turkish soldiers inside it.
"We have attacked and fully control Ghazlani base, we have also taken Tal al-Rayyan... and we're attacking Al-Maamun neighbourhood," said Sami al-Aridhi, a lieutenant general in Iraq's elite Counter-Terrorism Service.
He told AFP near the front line that IS attacked his forces with a suicide car bomb in Tal al-Rayyan, a village just outside Mosul, and that three other car bombs were found there.
Aridhi said the CTS, the most-seasoned force in Iraq, had suffered no losses since the renewed push on west Mosul was launched on Sunday.
He said some fighters had been wounded, however, including by the weaponised drones IS has increasingly resorted to in recent weeks.
AFP reporters south of Mosul said heavy artillery and mortar fire could be heard coming from the southern edge of the city while jets also conducted strikes.
While it was not immediately clear whether CTS forces would seek to push deep into the city, the move marks another landmark in the protracted Mosul operation.
The CTS spearheaded the weeks-long effort to retake areas of the city on the east bank of the Tigris River, only fully liberating it last month.
They met fierce resistance from Islamist militants defending their last major stronghold in Iraq and commanders have warned that the west bank, where IS leader Abu Bakr al-Baghdadi proclaimed his caliphate, would be even tougher.
After weeks spent redeploying across the vast theatre of operations, Iraqi forces rekindled the offensive on Sunday, with the airport the initial target.
"I can confirm that the airport is fully liberated," said Brigadier General Abbas al-Juburi, of the interior ministry's elite Rapid Response units that led the assault.
IS offered limited resistance at the airport and the nearby Ghazlani base, open and uninhabited areas that are difficult for them to defend in the face of the huge firepower deployed by Baghdad and its allies.
But the west bank of Mosul includes the Old City, whose narrow streets will be impassable for some military vehicles and oblige Iraqi forces to stage perilous dismounted raids.
The Islamist militants are completely surrounded in west Mosul and have little choice but to fight to the death.
Hashed al-Shaabi (Popular Mobilisation) units that have been in charge of a front in desert areas west of Mosul said Friday they were attacked by IS fighters coming from Syria.
IS militants have continued to harass Iraqi forces in areas that were retaken from them over the past two years.
On Friday, they attacked a border guard position near the Trebil crossing with Jordan, which lies about 500 kilometres (310 miles) west of the capital Baghdad.
"Daesh launched an attack with a suicide car bomb and gunmen on the 2nd border guard regiment near Trebil," an officer in the border guard told AFP, using an Arabic acronym for IS.
"The attack came from several directions and killed 15 border guards, including two officers," he said, speaking on condition of anonymity.
Iraqi aircraft carried out what were believed to be Iraq's first strikes on IS inside Syria Friday targeting militants responsible for recent bombings in Baghdad.
Over the border, IS is under attack on three fronts.
A US-backed alliance of Kurdish and Arab fighters has been pushing south towards the Islamist militants' main stronghold of Raqa.
Syrian government forces have been pushing east from Aleppo after regaining full control of the second city in December.
And a Turkish-backed rebel alliance has been pushing south from the Turkish border, ousting IS from Al-Bab after weeks of deadly fighting.
Turkish Prime Minister Binali Yildirim said that after Friday's twin attacks troops were carrying out "the most rigorous cleaning operations" in Al-Bab which he said was "full of bombs and hand-made explosives".
After a lightning advance, the rebels became mired in a drawn-out conflict in Al-Bab which proved to be the bloodiest fight in Turkey's campaign, where Ankara suffered most of its 71 losses thus far.