A dentist who believed he was possessed by evil spirits stabbed a faith healer at a centre which claims to treat black magic.

Ashfaq Choudhry, of Kensington Avenue, Watford, was arrested at the Tower of London after he stabbed Zakariyya Islam on September 14.

A witness reported hearing a disturbance at the Ruqya Therapy Centre, Whitechapel, which lasted around two or three minutes, before Mr Islam appeared and said: "Call the police, somebody stabbed me."

The 45-year-old, who was a member of East London Mosque, died around 30 minutes later.

Choudhry pleaded guilty to manslaughter on the grounds of diminished responsibility at the Old Bailey yesterday.

The Watford man confessed to officers and members of the public who restrained him after he tried to jump into the moat of The Tower of London.

The 43-year-old had knifed Mr Islam, a father-of-three, in the stomach and heart with a 25cm blade during the assault at the Ruqya Therapy Centre in east London.

Some of Mr Islam's relatives wiped away tears as a statement was read on behalf of the victim's wife Roma which told of the "unimaginable emptiness" she felt at his death.

Choudhry, a father-of-two, was suffering from a severe mental illness which affected his ability to form a rational judgement and to exercise self-control, prosecutor Timothy Cray told the court.

The defendant, who had told psychiatrists he felt "worthless", became disillusioned with the medication he was on and decided to explore alternative therapies, the court heard.

The Ruqya centre provides Islamic treatment for black magic, evil eye and Jinn (evil spirit) possession, according to its website.

Choudhry visited Mr Islam at the centre, which the court heard practices a form of spiritual therapy, three weeks before the killing, and said he was told he was possessed by spirits.

Linda Strudwick, mitigating, said: "He (Choudhry) genuinely believed what he had been told, that somebody had put evil spirits into him."

After his visit to the clinic Ms Strudwick said he told others: "Look at me, look at me, I'm a monster."

Sentencing Choudhry, the judge Richard Marks QC, the Common Serjeant of London, said Mr Islam, whom he described as an "outstanding individual", had been well-intentioned in his words and actions.

Addressing the defendant, he said: "There is no doubt that he was doing what he genuinely thought was best in order to alleviate your symptoms."

Choudhry was given a hospital order under the Mental Health Act, without a time limit.