Singapore on Friday hanged a Malaysian convicted of drug trafficking, the latest in what rights groups said was a series of executions prompting them to renew calls for the wealthy city-state to abolish the death penalty.

Singapore has some of the world's toughest anti-drugs laws, and airport customs forms warn arriving travelers of "death for drug traffickers" in no uncertain terms.

Human rights group Amnesty International and the U.N. human rights office have urged Singapore to halt executions and follow the example of neighboring Malaysia, where a newly elected government has vowed to end capital punishment by year-end.