As Iraqi forces entered west Mosul on Friday, for the first time since they launched their operation against the Islamic State group stronghold, curious children peered from behind front gates.

"Get back, get back, there are snipers," members of the Rapid Response units shouted at the children, who scattered back into their homes before IS bullets whizzed down into the muddy streets.

The Iraqi forces moved through Haw al-Jawsaq slowly, preceded by a small advance unit backed by attack helicopters.

Humvees drove through the narrow streets, with forces on foot looking out for vehicle bombs or suicide attackers, two favoured IS weapons.

In the first cluster of buildings stood a green mosque that Brigadier General Abbas al-Juburi of the rapid response units said was used by IS to counter the assault when it began earlier in the day.

The green paint on the mosque walls had been blasted away in places by gunfire and shrapnel, and two IS fighters lay dead in front of it.

Inside the neighbourhood, the walls bore signs of IS rule.

Its flag was graffitied on one house, while a large villa's outside wall was marked "reserved for the Islamic State".

On the wall next to a shop entrance was the warning: "Youth are forbidden from sitting here by order of the Hisba" (religious police).

The soldiers moved house to house, knocking on doors and asking residents for information about remaining fighters or hidden explosives.

As the troops secured the first part of the neighbourhood, civilians began to venture into the streets, waving and welcoming the soldiers.

Women ululated from inside their homes, while a group of men begged a soldier for cigarettes as he protested that he had none left.

- 'I'm feeling freedom' -

"I'm feeling freedom for the first time in more than two years," said Moqdad Ahmed, sporting the mandatory beard imposed by IS in territory under its control.

"For two years we lived with their orders, short trousers, beards, no cigarettes," he said.

"The women had to cover their faces and bodies, they couldn't go out without a male guardian."

He said he had kept his children home from school after IS transformed the curriculum to focus on weaponry and warfare.

"I pray, but with them you had to go to the mosque or they fined you, and you couldn't leave Mosul, you were trapped."

In another house, an elderly woman stood surrounded by her family, barely able to see or hear the arriving troops searching her courtyard.

"They're saying 'hello', grandma," said one of her granddaughters, like her fair and with striking blue eyes.

"Hello, hello, welcome," she waved at the troops.

Juburi said his forces had taken around two square kilometres (about three quarters of a square mile) inside Mosul by late afternoon in their assault targeting the Jawsaq, Danadan and Tayaran neighbourhoods.

He said there had been foreign fighters in the area and "most of them have been killed and the others fled north".

But IS did not appear to have fully withdrawn from Jawsaq, and firefights were ongoing as the sun started setting.

At one point sniper rounds came at soldiers as they crossed a street.

"Against the wall, against the wall," they shouted to the forces ahead to take cover.

And as they advanced, a huge blast from a car bomb sent black smoke and burning metal into the air in the distance.