The 40-year-old US citizen of Vietnamese origin was trying to leave Ho Chi Minh City on a flight to Sydney yesterday when he was caught with the drugs, the state-run Thanh Nien newspaper said.

He was arrested at the city's Tan Son Nhat international airport with the more than one kilogram of heroin in his luggage, the report said, adding police were investigating the case.

Vietnam's drug laws are among the toughest in the world and anyone found guilty of possessing more than around half a kilogram of heroin faces the death penalty.

In October 2012, a 61-year-old Filipina was sentenced to death after she was caught smuggling more than five kilograms of methamphetamine into the country.

And in June last year, a 23-year-old Thai design student was sentenced to death for trafficking three kilograms of amphetamines.

At present, there are more than 400 prisoners on death row, mostly for cases involving drugs or murder, but executions have declined in recent years.

No prisoners have been executed since July 2011, when Vietnam replaced execution by firing squads with lethal injections, as the country failed to import the lethal drugs needed to carry out the penalty.

In May this year, Vietnam amended the law on executions to allow locally-produced drugs to be used, potentially paving the way for a resumption of executions.

The new law comes into effect tomorrow but it is not clear whether executions will be immediately resumed.

Agence France Presse - June 26, 2013