Singapore has executed six men convicted of drug offences in October, despite pleas from Amnesty International and Malaysia, which recently pledged to abolish the death penalty.

Key points: Six men convicted of drug offences were executed in October

Six men convicted of drug offences were executed in October Appeals to Singapore for clemency were refused

Appeals to Singapore for clemency were refused Malaysia to abolish death penalty by end of the year

Prabu N Pathmanathan, a 31-year-old from Malaysia who had been on death row since 2014, was hanged at Changi prison on Friday morning.

A second man, reported to be Singaporean Irwan bin Ali, was executed alongside Mr Pathmanathan, following the "secret" hanging of Selamat bin Paki, according to the International Federation for Human Rights.

They were among six men executed in October, all on drug offences.

N Surendran, the lawyer for Mr Pathmanathan's family, told the ABC that Singapore authorities had unlawfully refused to consider a petition for clemency.

According to local media, the office of Singapore President Halimah Yacob had delivered a letter to Prabu's family in response to their petition, saying it was "unable to accede to [their] request".

Singapore President Halimah Yacob (left) refused clemency for Prabu N Pathmanathan. ( REUTERS: Wallace Woon )

Mr Surendran said his client "felt he had become a new man after the experience of being in prison" and had become "very spiritual".

"He wanted to live. He wanted to have another chance," he said.

Mr Surendran added that Singapore appeared to be shortening the notice given to prisoners "so they can execute with the minimum of fuss".

"It's extremely unfair and prejudicial to the prisoner and his family to give him practically less than a week notice of execution," he said.

Calls to abolish the death penalty

The case has fuelled a fresh push against the wealthy state's use of the death penalty.

Rachel Chhoa-Howard, Amnesty International's Singapore Researcher, said the death penalty contravened international law.

"It is time for Singapore to re-establish its moratorium on the death penalty and follow the Government of Malaysia's example, who have suspended all executions and announced plans to abolish the use of this cruel punishment for all crimes," she said.

"This cruel and irreversible punishment has no place in any society, as more than two-thirds of the world's countries have come to recognise."

Malaysia surprised many by abolishing the death penalty, making the announcement on October 10 — the World Day Against the Death Penalty.

It is expected to come into effect by the end of the year.

Drug offences accounted for the largest number of executions in Malaysia, which previously mandated capital punishment for crimes ranging from murder and kidnapping to drug offences and treason.

Amnesty International reported in March that 799 people on death row were convicted of drug trafficking, including 416 foreign nationals.

Singapore's Ministry of Home Affairs, which runs both the Singapore Central Narcotics Bureau and the Singapore Prison Service, could not be immediately reached for comment.

Reuters/ABC