McAlester, Oklahoma: The inmate who died of an apparent heart attack after a botched execution this week had had a Taser used on him in the morning of his execution, and doctors inserted an intravenous injection to administer lethal drugs into his groin after being unable to locate a usable vein in his arms, legs or feet, authorities said.

Prisons chief Robert Patton also disclosed in a letter to Oklahoma's governor on Thursday that death-row inmate Clayton Lockett deliberately cut his right arm before sunrise on Tuesday and refused to be restrained or to eat any food in the hours leading up to his death.

Clayton Lockett died of a heart attack. Credit:AP

Mr Patton recommended to Governor Mary Fallin that all executions in the state be put on hold indefinitely and called for an outside review of the state's capital punishment procedures.

The recommendation comes as Oklahoma state officials attempt to identify what went wrong with the execution of Lockett, 38, who was convicted of raping, shooting and ordering the live burial of a 17-year-old girl. Lockett writhed and convulsed as a toxic drug cocktail was administered and then died after the execution was called off.

Ms Fallin has ordered an internal review of the case to be conducted by the public safety commissioner. She also postponed the execution of another inmate, Charles Warner, who had been scheduled to die after Lockett.

Warner's lawyer Madeline Cohen called Lockett's death "torturous" and said no more executions should take place until a full investigation is conducted.

The Washington Post