The South African Police Service (SAPS) says a 21-year-old man will be charged with murder following the discovery of six bodies - five of them in an advanced state of decomposition - in a building in the main city, Johannesburg.

The local News24 site reports that the bodies were of six women.

"The [one] victim had her underwear below her knees. Her head and neck were covered with her skirt. All six had their hands and feet tied from behind," an unnamed eyewitness was quoted as saying.

Police said they launched an investigation after complaints of a foul smell coming from one of the rooms in the building.

The body of a woman was first discovered in the building, and her clothes matched the description of a woman reported missing earlier this month, a police statement said.

Five more bodies were found outside "where there is a makeshift workshop and rubbish dumpsters", the statement said.

"Unfortunately, the other five bodies are at the late stage of decomposition. They will be subjected to forensic analysis for identification," it said.

The 21-year-old man - who is believed to be the last person to have been seen with the woman - had been arrested, the statement added.

He is to be charged with six counts of murder.

Police have not yet given a possible motive for the killings.