By James Orr, guardian.co.uk

The Independent Police Complaints Commission (IPCC) today announced it was launching an investigation into the police handling of death threats to a teenager who was stabbed to death on Monday.

Arsema Dawit was repeatedly knifed in a lift in Matheson Lang House, the block of flats in Waterloo, south London, where she lived with her family.

Thomas Nugusse, 21, a student from Ilford, Essex was tonight charged with her murder. He will appear at Greenwich magistrates court tomorrow, Scotland Yard said tonight.

Members of the family said they had earlier told police that the 15-year-old had been assaulted by an obsessive man.

Yesterday, Scotland Yard confirmed that on April 30 police received a complaint that a man, aged 29 or 30, had assaulted her in a McDonald’s restaurant on April 16, making threats to kill her.

An officer spoke to Arsema at her school on May 12, but she claimed to have “no knowledge” of the incident.

Police contacted the teenager’s mother a week later, and the investigation was still ongoing when she was murdered.

Today’s announcement of came after Scotland Yard said senior officers would also examine the handling of the case.

In a statement released this afternoon the Met confirmed it too had commissioned an “internal review of our investigation into the crime allegation made by Arsema Dawit and her family on 30 April this year”.

It said this investigation would be overseen by the violent crime directorate and the directorate of professional standards.

Police arrested a man in connection with the killing on a footbridge over the river Thames as he threatened to kill himself shortly after the teenager was attacked, officers said.

Earlier, detectives were granted more time to question a 21-year-old man who was arrested over Arsema’s death.

The man was arrested on a footbridge over the River Thames as he threatened to kill himself shortly after the teenager was attacked, police said.

An IPCC statement said it had asked the Metropolitan police for the investigation to be referred to the commission.

“The family complained to the Metropolitan police that Arsema … was assaulted on April 30, five weeks before her murder,” the statement said.

“The IPCC awaits the referral, whereupon [it] will assess how the investigation should be carried out.”

A source close to the police inquiry said officers were not aware of a wider campaign of harassment against Arsema.

She was the 16th teenager to be killed in the capital this year, and the first female victim.

The attack came days after the Scotland Yard commissioner, Sir Ian Blair, vowed to do everything in his power to combat knife crime.