The 30 men and women, all Vietnamese, were found guilty of drug trafficking and given the death penalty while a further 59 defendants were handed sentences ranging up to life in prison in connection with the case, presiding judge Ngo Duc told AFP.
"This was Vietnam's largest ever trial in terms of defendants, the number of death penalties given out and the amount of heroin involved," Duc told AFP after the verdict was read out in the northern province of Quang Ninh - which borders China.
"Because of the large number of defendants and the seriousness of the case, the trial was held at the prison," judge Duc added.
The trial, which lasted 17 days, began on January 3 this year.
Investigators said that the defendants belonged to four international smuggling rings responsible for trafficking heroin and other drugs from neighbouring Laos into Vietnam and China since 2006.
Police busted the rings in August 2013 making mass arrests and seizing large quantities of illegal drugs.
Communist Vietnam has some of the world's toughest drug laws. Anyone found guilty of possessing more than 600 grams of heroin, or more than 20 kilograms of opium, can face the death penalty.
Convictions and sentences are usually revealed only by local media which is strictly under state control.
The "golden triangle" region of Laos, Thailand and Myanmar was formerly one of the world's top producers of illicit opium and heroin but has been overtaken by Afghanistan.
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