The US Supreme Court has delayed the execution of a convicted murderer in Missouri hours before a deadline, sending his case to an appeals court.

The ruling came three weeks after a botched lethal injection in Oklahoma last month stirred fresh debate about capital punishment in the United States.

All three executions that had been scheduled to take place after that event have since been delayed.

Russell Bucklew had originally been set to die at 12.01am (6.01am Irish time) this morning before legal proceedings late yesterday ended with a temporary stay issued by the Supreme Court.

The latest ruling came within hours of the end of that temporary stay.

Lawyers for the inmate had argued that a rare medical condition suffered by Bucklew that leaves him with growths on his head and neck put him at risk of excruciating pain during his execution, making it unconstitutional.

Bucklew was convicted in 1996 of murdering a love rival and raping a former girlfriend.

Death penalty states across the US have faced a barrage of legal actions challenging the origin of drugs used in lethal injections.

Oklahoma used an untested cocktail of drugs during the botched procedure because some drug suppliers have ceased making the substances usually used in executions available.

Some US states have turned to compounding pharmacies as a source of the drugs, but the future of that option is in doubt, as state governments review their execution procedures.

Despite the questions over lethal injection drugs, a recent study found that 59% of Americans remained in favour of capital punishment, with 35% against.