ISLAMABAD - The Supreme Court on Monday delayed for one week the execution of a man who had been declared insane by doctors, after rights groups urged the government to halt the hanging.

"A mentally-ill prisoner who was due to be hanged Tuesday morning has received a seven-day stay from the Supreme Court of Pakistan," Justice Project Pakistan, an independent rights group, said in a statement.

Imdad Ali had been scheduled to die at 5:30 a.m. on Tuesday in a prison in Vehari despite having been diagnosed with schizophrenia, it said.

"His execution was stayed pending a hearing on 27 September, but he could still be executed as early as next week," it said.

Human Rights Watch also urged Pakistan on Monday to halt the hanging, saying the execution would violate its international legal obligations.

Ali, who is aged around 50, was sentenced to death for the murder of a religious cleric in 2002.

HRW opposes the death penalty in all circumstances, said its country representative Saroop Ijaz.

"But in this case it also violates Pakistan's international legal obligations," Ijaz said, referring to the Convention on the Rights of Persons with Disabilities which Islamabad ratified in 2011.

"Imdad (Ali) has no insight into his punishment or condition or the idea of penalty. Executing someone who does not understand the punishment he or she is being awarded is simply harrowing and serves no criminal justice aim."

Separately, a psychiatrist who examined Imdad over several years and declared him insane in 2012 had said he was shocked at news of the imminent execution.

"He is a declared insane person," said Tahir Feroze Khan. "To hear about his death warrant is shocking news for me."

As per a medical report, Imdad's speech was incoherent, he frequently spoke and laughed to himself, and he suffered from paranoia and delusions of grandeur.

Despite being officially diagnosed with paranoid schizophrenia, the Lahore High Court last month rejected arguments that Imdad should not be executed because of his illness.

"His killing would signify in a grim way all that is wrong with the Pakistani justice system," added Ijaz.