Iraqi troops face fierce IS resistance near Tal Afar
Iraqi forces are facing fierce resistance in a small town where Islamic State militants who fled the city of Tal Afar have taken refuge.
One officer told Reuters news agency the fighting in Ayadiya was "multiple times worse" than the battle for Mosul.
Commanders have stepped up air and artillery strikes on IS positions and brought in reinforcements in response.
On Sunday the military said it had "fully liberated" Tal Afar, which was the last IS stronghold in north Iraq.
The announcement came a week after the Iraqi government launched an operation to retake the city involving some 50,000 personnel from the army, air force, federal police, special forces and the Shia-led paramilitary Popular Mobilisation force.
On Wednesday, the Popular Mobilisation's website reported that army and police Rapid Response Force units, backed by militiamen, had cleared a mosque north of Ayadiya and taken full control of the main north-south road through the town.
The gains came despite an increase in the severity of the fighting, with advancing troops repeatedly coming under attack from IS snipers, it added.
On Tuesday, army officers told Reuters that hundreds of militants armed with sniper rifles, mortars, heavy machine-guns and armour-piercing projectiles were holed up inside most houses and high buildings inside Ayadiya.
Col Kareem al-Lami, described breaching the militants' first line of defence in the town as like opening "the gates of hell".
"Daesh fighters in their hundreds are taking positions inside almost every single house in the town," he said, using a pejorative term for IS based on an Arabic acronym of its previous name.
"We thought the battle for Mosul's Old City was tough, but this one proved to be multiple times worst," he added. "We are facing tough fighters who have nothing to lose and are ready to die."
The government declared victory in Mosul in July, after an almost nine-month battle that left large areas of the city in ruins, killed thousands of civilians and displaced more than 900,000 others.
It is not clear whether any civilians remain inside Ayadiya, but the UN says 42,000 have fled Tal Afar district since April, half of them over the past two weeks.
Victory in Tal Afar would see IS dislodged from all but two areas in Iraq - around Hawija, 170km (105 miles) to the south-east; and from Ana to Al-Qaim in the Euphrates river valley, 220km to the south.
In a separate development on Wednesday, the governments of Iraq and Jordan said their only border crossing was open for the first time since 2015.
A joint statement said the move was possible because the highway between Amman and Baghdad had been "secured against attacks by criminal gangs".