The skeletal remains of a man wearing a suit were found tied up in a windsurfing bag, according to a man who saw the body.
Security guard Jason Mead, 38, said a man and woman walking their dog in Lovelinch Close, Peckham, south east London, yesterday morning alerted him and he saw the bag in some bushes.
Scotland Yard said the body had been placed at the scene some time in the past week.
An investigation has been launched into the death, which is being treated as unexplained.
A police spokesman said: "We believe that the skeletal remains were placed some time between 2pm on Friday August 5 and the early hours of August 10.
"The remains are of a white male, believed to be five feet tall. He was wearing a suit.
"At this extremely early stage, this is not believed linked to recent disorder."
A post-mortem examination is due to take place later.
A parking area at the side of a low-rise block of flats remained cordoned off with police tape today while two officers kept guard in a marked car.
Mr Mead, a security guard at a building site next to the flats, said the body was found by the two dog walkers behind some bushes in what he described as a brown windsurfing bag between 7am and 8am yesterday.
He said: "Two members of the public were walking their dog and the dog just went straight over there, it smelt something.
"The gentleman came up to me and said 'I think I've seen a dead body' so I went round there to check and see if there was.
"It was in a bag, like a windsurfing bag. I looked in one side and saw part of it.
"I don't know if it was a man or a woman, it was all tied up."
Mr Mead, who does not live in the area, said he had spoken to police and saw scenes of crime officers at the site all day yesterday.
Joan Viller, 72, a resident in the block of flats, said: "It is very upsetting, this is a very quiet area."