Singapore executed an Australian heroin trafficker on Friday despite a warning by Australia's prime minister that the hanging would sour relations between their countries.

The case has caused an outcry in Australia where opponents of the execution held vigils in cities around the country, with bells and gongs sounding 25 times at the hour of Nguyen's execution.

"I just think it's barbaric, it's wrong, it's disturbing," said Elizabeth Welch, a 54-year-old counselor at a vigil in Sydney.

Vietnam-born Tuong Van Nguyen, 25, was hanged before dawn despite numerous appeals from Australian leaders for his life to be spared. He received a mandatory death sentence after he was caught with 14 ounces of heroin at the city-state's Changi Airport in 2002, en route from Cambodia to Australia.

Nguyen's death came amid fresh debate about capital punishment in the United States, where North Carolina's governor denied clemency to a man who killed his wife and father-in-law. Kenneth Lee Boyd was executed by lethal injection early Friday in the 1,000th execution in the United States since the death penalty resumed in 1977.

Australian Prime Minister John Howard said his government would not take diplomatic action against Singapore. But he said the execution will affect relations "on a people-to-people, population-to-population basis."

Dressed in black, a dozen friends and supporters stood outside the maximum-security Changi Prison hours before the 6 a.m. hanging. Candles and handwritten notes containing sympathetic messages and calls for an end to Singapore's death penalty were placed outside the prison gates.

Nguyen's twin brother, Nguyen Khoa, entered the prison compound, but did not attend the execution. As he left, he hugged a prison officer and shook the hand of another. Nguyen Tuong Van had said he was trafficking heroin to help pay off his twin's debts.

Singapore says its tough laws and penalties for drug trafficking are an effective deterrent against a crime that ruins lives, and that foreigners and Singaporeans must be treated alike. It said Nguyen's appeals for clemency were carefully considered.

"We take a very serious view of drug trafficking — the penalty is death," Prime Minister Lee Hsien Loong said Thursday during a visit to Germany.

Nguyen was caught with more than 26 times the 0.53 ounces of heroin that draws a mandatory death penalty. The Home Affairs Ministry statement said the amount was enough to supply 26,000 doses of heroin, and had a street value of nearly $800,000.

Australia scrapped the death penalty in 1973 and hanged its last criminal in 1967, while Singapore has executed more than 100 people for drug-related offenses since 1999.

According to local media, Singapore has granted clemency to six inmates on death row — all Singaporeans — since independence in 1965.

A private Mass was held for Nguyen at a chapel on the grounds of a Roman Catholic convent. He was to be buried in Melbourne.

Physical contact between Nguyen and visitors had been barred in past days. But one of his Australian lawyers, Julian McMahon, said Nguyen's mother, Kim, had been allowed to hold her son's hand and touch his face during her last visit on Thursday.

"That was a great comfort to her," McMahon said.

Nguyen's supporters outside the prison included Gopalan and Krishnan Murugesu, teenage twin brothers whose father, Shanmugam, was executed in May after he was caught with 2.2 pounds of marijuana on Aug. 29, 2003, as he returned from Malaysia by motorcycle.