Singapore on Friday hanged a 45-year-old citizen for drug trafficking, the city-state's first execution of a woman in nearly two decades, officials said.

"The capital sentence of death imposed on Saridewi Binte Djamani was carried out on 28 July 2023," the Central Narcotics Bureau said in a statement.

She was convicted of trafficking "not less than 30.72 grams" of heroin, more than twice the volume that merits the death penalty in Singapore.

Djamani, who was sentenced in 2018, "was accorded full due process under the law, and was represented by legal counsel throughout the process," the bureau said in a statement.

"She appealed against her conviction and sentence, and the Court of Appeal dismissed her appeal on 6 October 2022," the bureau said, adding that her plea for presidential clemency was also rejected.

Djamani is the first woman to be executed in the city-state since 2004, the bureau said.

She is the 15th prisoner sent to the gallows since the government resumed executions in March 2022 after a two-year pause during the Covid-19 pandemic.

A local man, Mohd Aziz bin Hussain, 57, was hanged on Wednesday for trafficking about 50 grams of heroin.

Singapore 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.

Rights groups had urged the government to halt the executions this week, saying there was no evidence the death penalty acted as a deterrent to crime.

Singapore insists the death penalty has helped make it one of Asia's safest countries. (AFP)