Johannesburg - Child welfare authorities in South Africa are investigating the case of an Austrian man, who kept his 8-year-old son prisoner in his home for four years before he was discovered abandoned and hungry by neighbours, The Star newspaper reported Tuesday.

South Africans have been shocked by the story of the boy, dubbed Tarzan of Suburbia after he was discovered on November 17 at home alone in suburban northern Johannesburg, wearing tattered clothes and fearing contact with people.

Neighbours became aware there was a boy alone in the house when he pushed two 5 rand cent coins through a gap in the wall and asked employees from a business across the road to get him something to eat.

His father, 68, had collapsed five days earlier and called an ambulance, which took him to hospital.

He didn't alert the health services about his son, whom he had confined to the house and garden for four years, and allowed mainly to watch television and World War II videos.

The man, who is still in hospital, told The Star he didn't allow the boy out for security reasons and because he didn't want anyone to know he had a son, whom he reportedly fathered with a domestic worker that had since disappeared.

When friends came to visit the father, the boy was instructed to hide.

The neighbours who discovered the boy after convincing him to open the gate said he was wild in appearance, wore no shoes and seemed particularly frightened of older men.

The affair echoes two cases in Austria over the past two years in which a young girl and a young woman and her children were kept hostage by older men for years in their suburban homes.

Josef Fritzl, 73, from eastern Austria is accused of sexually abusing his daughter over 24 years and fathering several children with her in an underground dungeon before her discovery earlier this year.

Natascha Kampusch was kidnapped by a man at eight years old in 1998 and also kept behind lock and key before her escape in 2006. Her captor committed suicide.

There has been no suggestion so far of a sexual motive in the Johannesburg case. (dpa)