Mother in critical condition after trying to save four-year-old son in house fire

A house fire has claimed the life of a four-year-old boy after a blaze gutted a holiday house near the Snowy Mountains.

The family of six from Victoria had only arrived at Anglers Reach property, two hours south of Canberra, when a fire broke out in the open fireplace.

Five family members initially got out of the house safely before the 35-year-old mother ran back inside to retrieve her young son.

She was quickly overcome with smoke inhalation and remains in a critical condition with burns to her face and upper body.

The body of her son was found inside the home today.

A witness described the scene as horrifying.

“The woman was in complete shock, she was still screaming for her child, she just wanted her baby,” Daniel Ronde told 9NEWS.

“It was just so hot, the noise was like firecrackers continually going off”.

The woman's husband and his three children were uninjured.