The country has not executed anyone since 2011, when it decided to switch from firing squads to lethal injections on humanitarian grounds.
But it has found itself unable to source the chemicals used in the injections because of an EU ban on its factories exporting chemicals used in lethal injections
The state-run Laborer newspaper said the four were convicted yesterday in northern Vietnam for dealing in 50 kilograms of heroin.
Vietnam has some of the world's toughest drug laws.