Neighbours of a family whose home was gutted by a fire which also killed their four-year-old son have told of the frantic efforts to save the boy.

The home on Carnoustie Gardens in Meadow Springs, just north of Mandurah, was engulfed in flames just before 2pm on Sunday.

Firefighters battled the blaze in extreme conditions as WA baked under a heatwave, and the boy was pulled from a room and given CPR in a paddling pool before being taken by St John Ambulance to Peel Health Campus, where he died.

Nearby CCTV shows the boy’s sister and brother escaping, with the older boy running back into the house in an attempt to save his brother.

Neighbour Loretta Westcott told media at the scene on Monday it was “like hell on earth”.

“There was nothing we could do, we could not get in the house, even if we wanted to, even if we crawled, we would never have got in there,” she said.

“That smoke was so thick, you couldn’t even see the flames through the smoke it was so black, it was like hell on earth.

“I just kept talking to him and telling him to hang in there buddy, mum needs you, dad needs you, Santa’s coming, he wants to see you.”

The fire was believed to be accidentally lit, and arson squad investigators were investigating the home in the aftermath of the blaze.