The European Union and the UN Human Rights Office expressed regret Friday over the first execution of a man with nitrogen gas in the US state of Alabama.

The 27-nation European Union and the Geneva-based UN rights office say the death penalty violates the right to life and does not deter crime.

Kenneth Eugene Smith was put to death in Alabama on Thursday with pure nitrogen gas, a first-of-its-kind execution that placed the United States at the forefront of the debate over capital punishment.

Smith appeared to shake and convulse before being pronounced dead at an Alabama prison after breathing the gas through a face mask to cause oxygen deprivation.

“He was writhing and clearly suffering," Ravina Shamdasani, spokesperson for the UN Human Rights Office, said at a regular UN briefing in Geneva. "Rather than looking for novel, untested methods to execute people, let's just bring an end to the death penalty. This is an anachronism that doesn't belong in the 21st century.”

She said the UN human rights chief, Volker Türk, had written to authorities in Alabama about the issue, and said his office will continue to speak out and use “every tool in our toolbox" to prevent other states from doing so.

It was the first time a new execution method has been used in the US since 1982, when lethal injections were introduced and later became the most common method.

“According to leading experts, this method is a particularly cruel and unusual punishment,” the diplomatic service of the EU said in a statement. It also expressed concern that the number of executions in the US increased last year.

“Twenty-four people were executed in five states despite a steady, overall decline of the use of capital punishment in the US since 2020," it said. “We call for states that maintain the death penalty to implement a moratorium and move towards abolition, in line with the worldwide trend.”