Emergency services were called to the property in Lalor Park, about 35km west of Sydney’s city centre, around 1am local time, police said in a statement.

Two boys, aged two and four, were treated at the scene but died shortly after being taken to the hospital, while a 10-month-old girl was found dead after the fire was extinguished, police said.

A 28-year-old man, who frustrated police attempts to get into the property, was arrested and was being treated for fire-related injuries at the hospital under police guard, it said.

Homicide squad detectives have taken control of the investigation and are treating it as a “domestic-related homicide”, said homicide squad commander Detective Superintendent Danny Doherty.

“At this stage, it does appear the 28-year-old man is responsible for multiple deaths of young lives that have been tragically taken away,” Doherty told a press conference.

Four other children, aged from six to 11, were in stable condition in hospital, as well as the mother of the children, a 29-year-old who was being treated for smoke inhalation, police said.