Singapore has executed a man accused of co-ordinating a cannabis delivery, despite pleas for clemency from his family and protests from activists that he was convicted on weak evidence.

Tangaraju Suppiah, 46, was sentenced to death in 2018 for abetting the trafficking of one kilogram of cannabis. Under Singapore laws, trafficking more than 500 grams of cannabis may result in the death penalty.

Tangaraju was hanged on Wednesday morning and his family was given the death certificate, according to a tweet from activist Kirsten Han of the Transformative Justice Collective, which advocates for abolishing the death penalty in Singapore.

Although Tangaraju was not caught with the cannabis, prosecutors said phone numbers traced him as the person responsible for co-ordinating the delivery of the drugs. Tangaraju had maintained that he was not the one communicating with the others connected to the case.

At a United Nations Human Rights briefing on Tuesday, spokesperson Ravina Shamdasani called on the Singapore government to adopt a “formal moratorium” on executions for drug-related offences.

“Imposing the death penalty for drug offences is incompatible with international norms and standards,” said Ms Shamdasani, who added that increasing evidence showed the death penalty was ineffective as a deterrent.

Singapore authorities said there was a deterrent effect, citing studies that traffickers carried amounts below the threshold that would result in a death penalty.

The island-state’s imposition of the death penalty for drugs is in contrast with its neighbours. In Thailand, cannabis has essentially been legalised, and Malaysia has ended the mandatory death penalty for serious crimes.

Singapore executed 11 people last year for drug offences. One case that spurred international concern involved a Malaysian man whose lawyers said he was mentally disabled.

The Anti-Death Penalty Asia Network condemned Tangaraju’s execution as “reprehensible”.

“The continued use of the death penalty by the Singaporean government is an act of flagrant disregard for international human rights norms and casts aspersion on the legitimacy of Singapore’s criminal justice system,” the statement said.

Relatives and activists had sent letters to Singapore’s president Halimah Yacob to plead for clemency.

In a video posted by the Transformative Justice Collective, Tangaraju’s niece and nephew appealed to the public to raise concerns to the government over Tangaraju’s impending execution.

An application filed by Tangaraju on Monday for a stay of execution was dismissed without a hearing on Tuesday.

“Singapore claims it affords people on death row ‘due process’ but, in reality, fair trial violations in capital punishment cases are the norm: Defendants are being left without legal representation when faced with imminent execution, as lawyers who take such cases are intimidated and harassed,” Maya Foa, director of non-profit human rights organisation Reprieve, said.

Critics say Singapore’s death penalty has mostly impacted low-level mules and done little to stop drug traffickers and organised syndicates.

But Singapore’s government says that all those executed have been accorded full due process under the law and that the death penalty is necessary to protect its citizens.

British billionaire Richard Branson, who is outspoken against the death penalty, had also called for a halt to the execution in a blog post, saying that “Singapore may be about to kill an innocent man”.

Singapore authorities criticised Mr Branson’s allegations, stating that he had shown disrespect for the Singaporean judicial system as evidence had shown that Tangaraju was guilty.