By Jack Gramenz, Alex Mitchell and Melissa Meehan in Sydney

NSW has been “deeply wounded” by the devastating death of three young children, after their father allegedly frustrated attempts to rescue them from their burning home.

Premier Chris Minns forecast a 28-year-old man will be hit with “the most serious charges on offer” after children aged six, three and 10 months were killed in the fire at Lalor Park, in Sydney’s west early on Sunday morning.

Four other children – aged 11, nine, seven and four – and their mother are all being treated in hospital following the incident but are expected to survive.

Neighbours and emergency services got to the fire at about 1am on Sunday and rescued two boys, aged three and six, but they died a short time later.

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

The NSW premier 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,” Mr Minns 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.

Investigators will return to the property on Monday, with a lot of work to do to determine what happened, Homicide Detective Superintendent Danny Doherty told reporters.

“However, 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.

Detectives are treating the incident as a domestic-related multiple homicide and the 28-year-old man, who is yet to be charged, remains under police guard in hospital in a critical condition.

Attempts to enter the burning home were allegedly met with resistance as police officers and a neighbour heroically tried to rescue children from the fire, acting Superintendent Jason Pietruszka said.

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

“That male has been arrested.”

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

“There’s no other word for it,” Mr Pietruszka.

“It’s completely and utterly devastating.”