A Pakistani court has issued a death warrant for a schizophrenic man, his lawyers said, months after the country's top court halted the execution of another mentally ill prisoner.

Khizar Hayat, a 55-year-old former police officer, was sentenced to death in 2003 for shooting a colleague.

Lahore prison authorities pressed for the death warrant, which was granted by a sessions court, and the execution has been set for January 17.

The United Nations has previously called on Pakistan to protect mentally ill inmates, singling out Hayat as having "psychosocial disabilities".

The Justice Project Pakistan (JPP), which is managing his case, said it had filed an appeal against the court order.

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"We are taken aback by the court's decision to execute Hayat, while the case of Imdad Ali, who is also mentally ill and on death row, is still pending before the court," Rimmel Mohydin, spokeswoman for the JPP, told Al Jazeera.

"After our application against the court judgment, we are calling for a hearing again tomorrow [Thursday], so we are still hopeful."

Imdad Ali, also diagnosed with schizophrenia, was given a last-minute reprieve from execution by the Supreme Court in October, which said it was "inappropriate" to hang someone in his condition. A final decision on his fate remains pending.

JPP also said that despite eight years of treatment with powerful anti-psychotic medications, Khizar’s symptoms still remain as serious, and that his illness has been diagnosed as "treatment resistant" by medical experts.

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"Executing a mentally ill man would show that the fundamental rights of Pakistani citizens do not abide by international rights," Mohydin said.

Hayat's mother asked the court to suspend the death penalty for her son and direct the authorities to shift him to a hospital.

Pakistan has hanged more than 400 convicts since a moratorium on executions was lifted in 2014.

Pakistan halted executions between 2008 and 2014 due to pressure from international human rights groups. But it lifted the moratorium following a Taliban attack on a school in Peshawar in December 2014 that killed 150 people, nearly all of them children.

Last year, the execution of a Pakistani man - who was allegedly arrested as a juvenile and tortured into confessing to a murder - triggered an international outcry.