The man accused of frustrating efforts to rescue three children from a blazing house in Sydney’s west remains in a coma under police guard in hospital.

The children, aged six, three and 10 months, were killed in the fire at Lalor Park, in Sydney’s west on Sunday morning.

Four other children – aged 11, nine, seven and four – and their 29-year-old mother are all being treated in hospital following the incident.

They are expected to survive.

Neighbours and emergency services got to the fire about 1am to find flames shooting metres high out the windows.

They rescued two boys, aged three and six, but they died in Westmead Hospital a short time later.

The body of a 10-month-old girl was found inside the Freeman Street house after firefighters extinguished the blaze.

Police have said attempts by first responders and neighbours to enter the home were resisted.

“I can confirm during police attempts to get into the property, those efforts were frustrated by a male inside,” Acting Superintendent Jason Pietruszka said.

“That male has been arrested.”

The man is being widely named in the media as 28-year-old Dean Heasman.

Pietruszka said their efforts prevented the loss of more lives, but the fire and the death of three children would have a long-lasting impact.

“There’s no other word for it … It’s completely and utterly devastating,” he said.

Neighbours told the Nine Network that the surviving children had said the man ordered them to stay inside the house as it burned. One child said he fought to save his siblings.

“Dad tried to kill us,” the child allegedly told rescuers.

Other residents have told of seeing a man trying to drag frightened children back into the blazing house. They said he was shouting “leave me here to die”.

On Monday, NSW Premier Chris Minns said the state had been “deeply wounded” by the devastating deaths.

He forecast the 28-year-old man will be hit with “the most serious charges on offer”.

Minns said the “horrifying and senseless act” had outraged the entire state.

“These children deserved a loving home with safety and security, and instead, they’re gone,” he said on Monday.

“I can imagine the people of NSW feel enormous sorrow and deep sympathy with the surviving family members this morning, as we also show enormous care and gratitude to our emergency service workers … this is going to leave a deep wound on the state of NSW.”

Investigations will continue for some time, with dogs brought in to identify potential accelerants as police rake through the scene.

Homicide Detective Superintendent Danny Doherty said investigators would be back at the property on Monday, with much  work to do to determine what happened.

“At this stage, it does appear that the 28-year-old man is responsible for multiple deaths of young lives that have been tragically taken away,” he said on Sunday.

Doherty said the children’s mother was aware of what had happened and was sedated.

“They’ve just survived a traumatic fire incident where they’ve all been impacted physically, but they’ve also been impacted emotionally and mentally,” he said.

On Sunday, Fire and Rescue NSW Superintendent Adam Dewberry praised the work of those who were first on the scene.

“When you go to a house fire, you’re always expecting the worst [and] hoping it won’t be. But this was pretty confronting, absolute chaos,” he said.

Detectives are treating the incident as a domestic-related multiple homicide.

Heasman, who is yet to be charged, remains under police guard in hospital in a critical condition.

Police have not yet been able to speak to him.

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-with AAP