Singapore hanged two drug traffickers Thursday in what campaigners condemned as a "shameful and inhuman punishment", taking to four the number of executions in the city-state since March.
The latest executions come after the hanging of a mentally disabled man in April sparked international outrage, with the European Union and United Nations among those speaking out against it.
Singapore has some of the world's toughest anti-drugs laws, and insists that capital punishment remains an effective deterrent against trafficking despite growing pressure to abolish it.
Those executed Thursday were Kalwant Singh, a 31-year-old from neighbouring Malaysia, and Singaporean Norasharee Gous, 48, the prisons department said.
Kalwant's remains were taken back to Malaysia by his family on Thursday afternoon, prominent Singaporean rights campaigner Kirsten Han said.
Amnesty International said Singapore's use of the death penalty was "a blatant violation of human rights".
"We urge the Singaporean authorities to immediately stop this latest wave of hangings and impose a moratorium on executions as a step towards ending this shameful and inhuman punishment," said the group's Emerlynne Gil.
Phil Robertson, deputy Asia director at Human Rights Watch, added that Singapore was flouting international norms on rights that prohibit "cruel" punishments.
Recent drug busts in the city-state "show just how hollow Singapore's claims are about the supposed 'deterrent' effect of these cruel executions", he said.
Kalwant and Norasharee were convicted in 2016 of trafficking heroin in the same case.
The Malaysian lodged a last-ditch appeal Wednesday, with his lawyers arguing he provided information that helped authorities arrest a key suspected drug trafficker.
But a three-judge panel dismissed the appeal, saying drug enforcement officials did not use any information he provided to arrest the suspect.
After a hiatus of over two years, the city-state resumed executions in March with the hanging of a Singaporean drug trafficker, and activists fear more will be conducted in the coming months.
In a recent BBC interview, Home Affairs and Law Minister K Shanmugam defended Singapore's position on the death penalty, saying there is "clear evidence that it is a serious deterrent for would-be drug traffickers".