Geneva, Switzerland - UN rights chief Volker Turk on Thursday urged Tennessee not to make a new attempt to execute Christa Pike after she survived two lethal injection doses.

Convicted murderer Pike (50) was being treated in a hospital, her lawyers said, following Tennessee's second failed execution in months.

"The case of Christa Pike lays bare multiple reasons why the death penalty should be abolished," the UN rights office said on X.

"The prolonged suffering – physical and mental – arising from multiple failed execution attempts is abhorrent, and cruel. And there are key fair trial questions still unresolved."

On Wednesday, the Supreme Court cleared the way for Pike to become the first woman to be executed in Tennessee in 200 years – but the attempt failed.

Turk "calls on the state authorities not to pursue any further attempt to execute Pike", the UN rights office said.

"We are also troubled by the increase in the number of executions in the United States," it added. "The death penalty has no place in any society."

The failed attempt to execute Pike prompted Tennessee authorities to halt capital punishment for the rest of the year.

Pike was 18 when she and her boyfriend beat and killed Colleen Slemmer (19) at a job training camp for young people.

The killing gained national attention after Slemmer's body was found with a pentagram, often seen as a satanic symbol, carved in her chest.

Pike's lawyers argued she should be granted clemency due to her young age and mental health issues at the time of the killing.

In the US, 18 women have been executed since 1976, according to the Death Penalty Information Center.