Singapore executed a 39-year-old man who was convicted of trafficking heroin, the city-state's fifth hanging this year and the third in just over a week, authorities said on Thursday.

Mohamed Shalleh Adul Latiff was sentenced to death for possessing around 55 grams of heroin "for the purpose of trafficking" in 2019.

His punishment was carried out on Thursday, the Central Narcotics Bureau (CNB) said in a statement.

According to court documents, Mohamed Shalleh worked as a delivery driver before his arrest in 2016. During his trial, he claimed to have believed he was delivering contraband cigarettes for a friend to whom he owed money.

He became the 16th prisoner sent to the gallows since the government resumed executions in March 2022 after a two-year pause during the Covid-19 pandemic.

The execution comes less than a week after Singapore executed the first woman in nearly 20 years for drug trafficking despite condemnation from rights groups.

Saridewi Binte Djamani, a 45-year-old Singaporean, was executed on Friday for trafficking around 30 grams of heroin.

A local man, Mohd Aziz bin Hussain, 57, had been hanged two days earlier for trafficking about 50 grams of heroin.

The United Nations last week denounced the hangings and called for Singapore to impose a moratorium on the death penalty.

Despite growing international pressure on the issue, Singapore insists that the death penalty is an effective deterrent against drug trafficking.

The wealthy financial centre has some of the world's toughest anti-drug laws -- trafficking more than 500 grams of cannabis or over 15 grams of heroin can result in the death penalty.