UPDATED 10.04am: Diligent neighbours saved a Christchurch man from a fire in his own kitchen.

They rang the fire service just before 10 last night, after hearing the man's fire alarm sounding in Champion Street.

Crews managed to break down the door to find the man asleep and the kitchen on fire from a pot left on the stove.

Fire service Shift Manager Riwai Grace says the resident probably shouldn't have been cooking.

"One of the guys from the crew said he's just got into the country off an international flight, so he was probably a bit tired and he shouldn't really have been cooking.

"Luckily he's got good neighbours."

A fire which all-but destroyed a Christchurch property is thought to have started outside.

Neighbours claim the occupants had only moved in a week ago - with witnesses stating people had set off fireworks near the house shortly before the blaze started.

Senior fire management risk officer Mark Thomas says they're still investigating the cause, but it's very lucky no one was hurt.

"Oh, the property's quite severely damaged, particularly at the back to such an extent - because of its age - I would suspect it won't be repairable."