CHILD killer Robert Black has died in prison in Northern Ireland.

Black, who was convicted of the murders of nine-year-old Jennifer Cardy from Northern Ireland; Sarah Harper, 10, from England, and 11-year-old Susan Maxwell and five-year-old Caroline Hogg, both from Scotland, died of natural causes in Maghaberry prison.

He was 68.

HeraldScotland: Robert Black, pictured in 2011, when he was convicted over the murder of Jennifer Cardy in Ballinderry, County Antrim

Black abducted, abused and murdered his victims while working as a delivery driver in the 1980s, before eventually being caught by an off-duty policeman as he tried to kidnap another young girl.

In a statement, the Northern Ireland Prison Service confirmed that a 68-year-old prisoner had died at the high-security jail.

It stated: "While this is not being treated as suspicious, the Prison Service has informed the Police Service of Northern Ireland (PSNI) Coroner, and Prisoner Ombudsman.

"It would not be appropriate to comment further at this time."

HeraldScotland: L-R: Caroline Hogg, Susan Maxwell, Sarah Harper and Jennifer Cardy

Black, originally from Grangemouth, is considered by police to be one of the most dangerous men in British criminal history.

He was convicted of the murders of Sarah, Susan and Caroline in 1994 and sentenced to life imprisonment.

He was subsequently convicted of the murder of Jennifer Cardy, 30 years after her death, at Armagh Crown Court in 2011 and transferred from Wakefield prison in England to Northern Ireland. 

It emerged during the trial that Black had been a suspect in the original investigation decades before but police found no reason to arrest him.

He was also thought by police to be responsible for at least another four child murders in the UK, and possibly others abroad.