Emergency services were called to the fire in Curzon Pl in Parklands about 6.10am on Monday.
Caity Leah who lives opposite the house told Newstalk ZB's Chris Lynch she woke up to a fire alarm and land banging and popping noises.
She said she saw an elderly man being carried out of the burning house and onto the street.
"It was extremely intense to wake up to and I feel for everyone involved."Leah said the elderly person was very upset.
The elderly man's neighbour, Pete, said he banged on the back door to try and tell the man to get out of the house while firefighters did the same at the front door.
He said the man came to the front door but seemed unaware of what was happening and attempted to run back into the house, but was pulled to safety by a firefighter.
"They [firefighters] were smashing on the door. He came to the door and tried running back in the house. One of them grabbed him and dragged him out," said Pete.
He does not know the elderly man who he said kept to himself.
A St John spokesman said the man was taken by ambulance to Christchurch Hospital with serious injuries.
The two-storey flat was extensively damaged on the lower level but the fire has now been extinguished.
"The building was well involved on arrival," the FENZ spokesman said.
By about 6.30am, firefighters were still working to extinguish the blaze.
Officers were dampening down the fire at about 7.30am.
Meanwhile yesterday, fire crews battled a large house blaze in Pōkeno, Waikato.
Emergency services rushed to the scene after multiple reports of a fire that could be seen from State Highway 1, south of Auckland.
A huge plume of black smoke could be seen billowing from the blaze, which was first reported about 2.46pm. There were no reports of any injuries.
-Matt Slaughter and NZ Herald
