Tangaraju Suppiah, 46, was hanged at Changi Prison at dawn on Wednesday, one day after the courts rejected a last-minute appeal, the BBC reports.

On Tuesday, the UN high commissioner for human rights had urged the Singaporean government “not to proceed with his execution”, warning that imposing the death penalty for drugs offences is “incompatible with international norms and standards”.

Mr Suppiah was sentenced to the mandatory death penalty in 2018 following proceedings that human rights campaigners said violated international human rights law and standards.

He was accused of coordinating with two men to traffic one kilogram of cannabis into Singapore in 2013, but he never received the drugs that were allegedly ordered by him.

Mr Suppiah, a Tamil speaker, was convicted mainly based on statements that he gave during police interrogation with no lawyer or interpreter present, as well as on the testimony of the other men accused of the crime, who appeared as prosecution witnesses.

Ming Yu Hah, Amnesty International’s deputy regional director for east and south-east Asia and the Pacific, said: “This unlawful execution shows yet again the staggering failure of Singapore’s stubborn embrace of the death penalty.

“The many flaws in the case, from lack of access to legal counsel and of interpretation from the point of arrest to the lack of disclosure of key evidence from the prosecution, as well as the continued reliance on the mandatory death penalty renders this execution arbitrary under international human rights law.

“The country’s highly repressive drug control law includes the mandatory death penalty, which means that judges are not allowed to take into consideration possible mitigating circumstances at sentencing, including circumstances of the crime, background of the defendant or other factors relevant to the case.

“This is a punishment that Singapore’s neighbour Malaysia is in the process of fully abolishing to advance the protection of the right to life.

“Singapore’s punitive drug policies have failed not only to tackle the use and availability of drugs in the country, but also failed to offer effective protection from drug-related harm.

“The government of Singapore must take note of the growing trend around the world towards abandoning the death penalty and act accordingly, first by establishing an official moratorium on all executions, then moving towards full abolition.”