A paranoid schizophrenic who beheaded his flatmate after "vanishing" from the mental health care system has been imprisoned for life.

Karl Addo, 30, killed Sergio Marquez, 23, at the flat they shared in Bournemouth in July 2012 in a "frenzied attack".

Addo stabbed and decapitated his flatmate in the "prolonged, horrific and very violent attack" in he belief Marquez was part of a gang with special powers who wanted to torture and kill him.

Addo, who had suffered from mental health problems for years, pleaded guilty to manslaughter on the grounds of diminished responsibility.

He was sentenced to be detained for life with a minimum six and a half years at Broadmoor high security hospital in Berkshire. The judge at Bournemouth Crown Court warned Addo he may never be released from hospital as he is too dangerous.

The court heard how Addo had "disappeared" from the Huntley mental health centre in London on October 2011 having voluntarily checked in as a patient there. The day after he walked out of the clinic, a tribunal declared he should be sectioned under the Mental health act, but he could not be found.

Addo moved to Bournemouth in May 2012 and killed the Spanish student and waiter Marquez 14 months later. In between these dates he was ejected from Heathrow airport and spotted sleeping rough in Marylebone station in London.

Speaking outside the court, the victim's mother, Maria Marquez Torres, 43, said: "I cannot understand how someone like this who was known to have such problems has not been dealt with properly. More should have been done to protect people from this man.

"If he was so ill, how has he been allowed to live in a rented apartment with other people? It was clear that it was only a matter of time before something like this happened and he killed someone.

"I want him put away for life. Whatever punishment he gets it will not be enough. To me he is the devil. Because of what he did my life no longer makes any sense - it has been ripped in two."

The headless and disembowelled body of Marquez was discovered by two other flatmates at the address. Addo fled the flat when the others returned and was later found by police covered in blood.

Det insp Stewart Balmer, of Dorset Police's Major Crime Investigation Team, said: "This was a horrific offence committed against a young man who had come to the UK to broaden his horizons and improve his English.

"This is a tragic loss of life and it has deeply affected all those who knew Sergio.

"Today's proceedings have brought to an end the investigation and will hopefully give the family some closure."