SINGAPORE, July 25 (AFP) - Singapore is set to hang two drug convicts this week, including the first woman to be sent to the gallows in nearly 20 years, rights groups said Tuesday, while urging the executions be halted.

Local rights organisation Transformative Justice Collective (TJC) said a 56-year-old man convicted of trafficking 50 grams (1.76 ounces) of heroin is scheduled to be hanged on Wednesday at the Southeast Asian city-state's Changi Prison.

A 45-year-old woman convict who TJC identified as Saridewi Djamani is also set to be sent to the gallows on Friday. She was sentenced to death in 2018 for trafficking around 30 grams of heroin.

If carried out, she would be the first woman to be executed in Singapore since 2004 when 36-year-old hairdresser Yen May Woen was hanged for drug trafficking, said TJC activist Kokila Annamalai.

TJC said the two prisoners are Singaporeans and their families have received notices setting the dates of their executions.

Prison officials have not answered emailed questions from AFP seeking confirmation.

Singapore imposes the death penalty for certain crimes, including murder and some forms of kidnapping.

It also has some of the world's toughest anti-drug laws: trafficking more than 500 grams of cannabis and 15 grams of heroin can result in the death penalty.

At least 13 people have been hanged so far since the government resumed executions following a two-year hiatus in place during the Covid-19 pandemic.

Rights watchdog Amnesty International on Tuesday urged Singapore to halt the impending executions.

"It is unconscionable that authorities in Singapore continue to cruelly pursue more executions in the name of drug control," Amnesty's death penalty expert Chiara Sangiorgio said in a statement.

"There is no evidence that the death penalty has a unique deterrent effect or that it has any impact on the use and availability of drugs.

"As countries around the world do away with the death penalty and embrace drug policy reform, Singapore's authorities are doing neither," Sangiorgio added.

Singapore insists that the death penalty is an effective crime deterrent.