By Tim Gaynor

PHOENIX (Reuters) - Arizona's top court issued a stay of execution on Tuesday for death row inmate Samuel Villegas Lopez, a day before he was scheduled to die by lethal injection, to address claims that he had been denied a chance at a fair clemency hearing.

Villegas Lopez was sentenced to death for raping 59-year-old Estafana Holmes and stabbing her to death in a violent, drawn-out assault at her Phoenix apartment in 1986.

The Arizona Supreme Court rescheduled his execution for June 27 so that attorneys could address claims that he was denied a fair clemency hearing because some members of the state clemency board had not received a mandated four-week training course.

"We conclude that the interests of justice are best served by staying the pending execution and forthwith issuing ... a new warrant of execution, for June 27," the court said in its ruling.

"The period between now and the new execution date will allow training of new board members and a clemency hearing to be subsequently held by the board," it added.

He had been due to die by lethal injection at 10 a.m. on Wednesday morning, at the state prison in Florence, some 60 miles southeast of Phoenix.

Lopez would be the fourth Arizona inmate to be executed this year in Arizona, and the 32nd since the state reinstated the death penalty in 1992.

Last month, a controversy erupted in the state over the execution of convicted killer Thomas Kemp using the single drug pentobarbital. Kemp's lawyer Tim Gabrielsen, who witnessed the execution, said that his client began to "shake violently" after the drug was injected.

Gabrielsen said he was concerned that his client might have suffered cruel and unusual pain before he died. A corrections official who also witnessed the execution disputed Gabrielsen's account.

(Editing by Cynthia Johnston and Lisa Shumaker)