A "lovely" six-year-old boy was found dead inside the bedroom of his Brisbane home after a fire broke out close to where he was sleeping in the early hours of the morning.

The schoolboy - just weeks from his seventh birthday - was unable to escape the blaze when his mother, father and another child made their way out as the fire consumed the Clayfield home about 4am today.

The community has been left devastated, with one local describing the harrowing moment she saw his mother realise her son could not be saved from the blaze.

"The realisation she couldn't go back into the home to save him is something I will never ever forget," Jenn Davidson told 9News.

"Devastating - an awful thing to witness.

"We as a community are just in shock. It's a heart breaking experience for all involved.

She described the six-year-old as a "lovely boy".

"Beyond words," she added.

Superintendent Paul Durston from Queensland Fire and Emergency Services said by the time firefighters arrived the whole house was ablaze.

"The crews were met by a lot of smoke and a lot of heat, it was very difficult to make entry through the front door but they eventually made entry through there," he said.

Heat from the fire caused the windows to break, causing explosions to ring out.

Superintendent Durston said as older style Queenslanders get quite cold, residents will close their windows which can increase the risk of a fire quickly developing.

"It gets very hot internally and then the windows fail ... the fire starts to rage quite quickly," Superintendent Durston said.

Upon entry, fire fighters struggled to get through the property, eventually locating the body of the young boy in his bedroom.

"Firies absolute priority was not to even consider their own lives that stage and just do their very best to make entry into the back bedroom. but the fire was so intense it was impossible at that point," Mark Halverson from QFES said.

The cause of the fire is unknown. An investigation has been launched.

Due to the extensive damage to the building it is unclear whether the home had working smoke alarms.

"We have no reason to believe there weren't," Mr Halverson said.

"Interconnected smoke alarms that will sound in the bedrooms even if the fire has started elsewhere provide that early warning so they are a vital safety feature for all occupants of dwellings."

Mr Durston said while emergency crews are glad they saved the lives of the three residents, they are devastated by the loss of the child.

"Very difficult for crews when they can't save all of the lives inside because of the heat and the fire so the crews are quite distraught," he said.

"They're not good scenes but the crews did the best they could when they arrived and we had 26 firefighters here that worked tirelessly to try and get this situation under control as quickly as they could."