A South Dunedin woman has spoken of helping a man to safety in a house fire which claimed two lives this morning.

Emergency services were alerted to the blaze in Wesley St about 5.15am and arrived soon after to find the property well alight.

Neighbour Mel Ryall, who lives directly behind the single-storey wooden house, said she noticed the blaze when she came back from dropping her husband at work about 5.10am.

"I saw smoke coming out, so I parked the truck and got my stepson who was home at the time to ring the fire brigade."

She then remembered a man who needed assistance walking lived in the front flat of the burning property.

"So I ran down the driveway. He was yelling, 'fire, help', and needed help getting out because he didn't have his walking frame with him."

Ryall put her arms around the man and got him to safety.

"I was concerned the fire was getting close to the neighbour's window because it was at the side of the house.

"I went to knock on the next door neighbour's door to wake them up. They had fire damage too."

Ryall said she felt for the family who had lost lives.

"I hate to think if we were all still sleeping and my husband hadn't have gone to work, what could have happened.

"The houses are so close together. I'm just glad ... there weren't some more lives lost."

There was considerable fire damage at the side of the building and there was also a hole in the roof.

Fire communications spokesman Rewai Grace said the first firefighters arrived at the scene about three minutes after they were alerted to the incident.

"On the way there, we noticed there was unfortunately a good glow in the morning sky, so we called in another engine."

The house was well ablaze upon their arrival, Grace said.

Crews remained at the scene where they were working to get the fire under control and would be there for most of the day.

Fire investigators would begin work when the property was safe to enter.