A Malaysian man convicted of smuggling drugs into Singapore was executed Wednesday despite appeals from human rights advocates and global business leaders who said he should be spared because he suffered from a mental disability.

       Nagaenthran Dharmalingam, 34, was executed by hanging, according to his attorney, M. Ravi. He was caught in 2009 with about 1.5 ounces of heroin strapped to his thigh as he entered Singapore from Malaysia.

       His lawyers and rights groups said that Mr. Nagaenthran suffered from an intellectual disability and was not fully capable of understanding his actions and that he was coerced into carrying the drugs.

       Among those who urged Singapore to stay his execution were Malaysia’s prime minister, Ismail Sabri Yaakob; the British billionaire founder of the Virgin Group, Richard Branson; and the Malaysian entrepreneur and chief executive of AirAsia, Tony Fernandes. More than 100,000 people signed a petition urging Singapore’s president, Halimah Yacob, to pardon him.

       “Nagaenthran Dharmalingam’s name will go down in history as the victim of a tragic miscarriage of justice,” said Maya Foa, director of Reprieve, one of the rights groups. “Hanging an intellectually disabled, mentally unwell man because he was coerced into carrying less than three tablespoons of diamorphine is unjustifiable and a flagrant violation of international laws.”

       Mr. Nagaenthran was sentenced to death a decade ago. On appeal, the courts rejected his argument that his sentence should be overturned because of his disability. Singapore’s Ministry of Home Affairs said that Mr. Nagaenthran received a fair trial and that the court concluded his actions were “the working of a criminal mind.”

       “Nagaenthran was found to have clearly understood the nature of his acts, and he did not lose his sense of judgment of the rightness or wrongness of what he was doing,” the ministry said.

       According to an affidavit submitted by Mr. Nagaenthran’s brother last year, his mental state had deteriorated while in prison, leaving him disoriented and unable to recollect conversations that had taken place minutes earlier.

       Singapore’s High Court granted a stay in November, but the Court of Appeal cleared the way on Tuesday for the execution to proceed. It was carried out early Wednesday.

       Singapore, an island nation of nearly 6 million that has some of the world’s harshest narcotics laws, contends that the death penalty is a deterrent to drug smuggling. The United Nations High Commissioner For Human Rights said Monday that it was “deeply concerned” by an increase in executions in Singapore, and joined in urging that Mr. Nagaenthran be spared.

       “The use of the death penalty for drug-related offenses is incompatible with international human rights law,” the human rights office said.