A home intruder has died after an altercation with a resident at a house in Sydney's south-west.

Around 7.30am on Sunday the 44-year-old father of the home on Westwood Court in Harrington Park awoke to the sound of his dog barking.

Police say he went to investigate and challenged a male intruder in the loungeroom.

A physical struggle ensued and the intruder lost consciousness.

The resident's wife alerted neighbours and two members of the public commenced CPR on the unconscious man.

Paramedics soon arrived but were unable to revive him.

The male resident was taken to Narellan Police Station but was released on Sunday evening without charge.

A man points detectives to the house where the invasion occurred. ( ABC )

Detective Inspector Shane Woolbank said people are "entitled to their home" and can use reasonable force to protect themselves and their property.

He said police were unable to determine the identity of the intruder.

"We are appealing to anyone who has information on this person," he said.

The man was aged in his late 20s to early 30s, with muscular build and was 175-180 centimetres tall. He had a ginger-like moustache and beard and was wearing a blue sleeveless top and grey knee-length shorts, but no shoes.

He had two tattoos — one on the upper inside of his left arm which is not in English, and one on his upper left chest which reads: "True to ourselves is our true honour."

He also has a scar on his left shoulder.

The Harrington Point house where the intruder died in the loungeroom. ( ABC News )

Nearby resident Dominic Lombardo was in his backyard and heard banging and heavy breathing next door this morning.

"I jumped up on my retaining wall and I saw the guy … he was barefoot and scaled the back fence, bolted across the road and scaled another fence," he said.

"Five minutes later all hell broke loose with police and ambulance."

Neighbour Mariano Moscabenny said he heard a noise and saw a man running barefoot from a nearby house up to the dog park where he tried to jump the fence.

"He didn't look right, he looked nervous, anxious and making all these sounds. Funny noises, just in hysterics and he didn't really make eye contact with anyone.

"I feel sorry for the person involved there [the resident]. It's one of those moments where you don't really know what to do at that time at that situation.

"I wouldn't like that to happen to me. I've got a young family as well, you want to make them safe and protect them."