The dismembered body of a missing teenager has been found dumped near a stairwell on a housing estate.

Officers found the body of Rochelle Holness, 15, at Milford Towers, Catford, south London, on Wednesday. It is thought she had been abducted.

Police were alerted by ambulance crews who had been called to reports a man had injured himself. Police found body parts in bin bags outside the flats.

A man and woman, both aged 47, are being questioned by police.

Distraught family and friends have taken flowers to the scene, which is behind a police cordon, and forensic experts have been seen leaving with evidence bags.

A man has pleaded guilty to murdering a 15-year-old girl whose dismembered body was found dumped on a housing estate.

John McGrady, 48, of Milford Towers, Catford, south London, carried out the attack on Rochelle Holness last September, the Old Bailey heard.

She vanished after going out to call her boyfriend from a phone box near her home in Lewisham, south London.

Her body was found in bin bags near a stairwell on the Milford Towers estate. McGrady will be sentenced on 15 May.

Her attacker was said to be a heavy-drinking handyman with previous convictions for rape and false imprisonment.

The 48-year-old was remanded in custody at the Old Bailey and warned he would receive a life sentence at the next hearing.

Detective Inspector Tim Grattan-Kane said: "John McGrady is an absolute danger to any young woman, a spectacularly dangerous and violent man who when a desire befalls him he decides to inflicted it on innocent victims.

A suspected serial rapist who attacked women for over two decades was yesterday sentenced to die in jail after being convicted of murdering and dismembering a teenage girl. John McGrady was given a full life sentence for murdering 15-year-old Rochelle Holness on a south London council estate in September last year.

McGrady, 48, had been a sex offender for 22 years, with convictions for rape and indecent assault, before he butchered the teenager. Last night Rochelle's family called for a change in the law so that communities are told when serious sexual offenders are living among them.

McGrady, a former butcher, pounced on Rochelle as she used a call box to phone her boyfriend. He is believed to have abducted her and strangled her before dismembering her body with a hacksaw and placing the parts in five bin bags, which he left near a rubbish chute in Milford Towers, Catford, south London, where he lived.

Detectives fear McGrady is likely to have attacked women between his last release from prison in 1997 and his arrest last year. A police source told the Guardian it bordered on unbelievable that McGrady had not committed other offences in that period and victims were urged to come forward.

Rochelle's mother, Jennifer Bennett, shouted "Rot in hell" as McGrady was taken from the dock at the Old Bailey.

Judge Stephen Kramer told him: "You must have been motivated by a sexual desire and when you are drinking you are, and continue to be, a dangerous predator to women, especially young women.

"The sentence will ensure you will never have the opportunity to prey on young women again. You cruelly took the life of that young girl and left her family and her mother bereft."

A postmortem examination was unable to establish whether Rochelle had been sexually assaulted. A psychiatrist who examined McGrady concluded that a sexual motivation could not be discounted.

Rochelle lived with her mother and two brothers in Catford and was a sociable girl, studying for GCSEs. She left the flat after her mobile phone ran out of credit.

McGrady was caught after he confessed to a girlfriend in a note he left after he slashed his wrists in a failed suicide attempt. He had a long and violent criminal history, and was jailed for six years in 1988 after being convicted of raping two young women. In 1993 he was convicted of attempting to abduct a young woman at knifepoint and was jailed for five years, a relatively high sentence reflecting the belief that he was interrupted before he could sexually assault the woman.

But McGrady had also been acquitted of rape three times in 1984, telling juries the women had consented. In one case he had worn a balaclava and used a knife.

Ms Bennett and Rochelle's father, Denroy Holness, told the Guardian the criminal justice system had failed in McGrady's case. "We question why we do not have the right to know about these dangerous people living among us, until they have committed such dreadful acts." The so-called Sarah's law has previously been opposed by the police after it was championed by a tabloid newspaper, leading to attacks on sex offenders and innocent people.

Rochelle's parents, in a statement read outside court, said: "We hope these events send out a clear message to the country that sex offenders and murderers must in future be properly sentenced, treated and supervised on release, otherwise there will be many more victims. We pray that while serving his sentence, McGrady receives treatment so that he may truly take full responsibility for his actions and bring himself to explain why and how he did this to Rochelle."

The family criticised two tabloid newspapers which published lurid and false details about the case. The Sun wrongly claimed Rochelle had been strapped to a table then dismembered while still alive. The family has complained to the Press Complaints Commission and said the newspaper had been as cruel to them as the man who murdered their daughter. "We hope those responsible for causing us so much unnecessary pain will today feel the shame that has so far been absent; for their behaviour has been as inhumane as John McGrady's."

Outside court, Detective Inspector Tim Grattan-Kane branded McGrady "evil", and said: "He should not have been on the streets, but hindsight is a wonderful thing. There was nothing that would have given the judge the sentencing powers to keep him off the streets for ever."

The Home Office confirmed that McGrady had not been under supervision.

The sex offenders register was introduced just after he was released in 1997 and a spokesperson said measures had been introduced to protect the public from highly dangerous offenders, including "indeterminate public protection sentences, in which violent and sexual offenders can be held in custody for as long as is necessary".