Dead women walking: Vietnam sentences 30 heroin smugglers to death including NINE females

Justice en masse: Some 89 defendants are each flanked by two police officers as they are sentenced for heroin smuggling after Vietnam's biggest-ever drugs trial

'Because of the large number of defendants and the seriousness of the case, the trial was held at the prison,' Mr Duc added after the 17-day trial.

Investigators said the defendants belonged to four international smuggling rings responsible for trafficking heroin and other drugs from neighbouring Laos into Vietnam and China since 2006.

'All the defendants are Vietnamese and most of them came from Vietnam's northwestern provinces,' court clerk Nguyen Trung Hieu told AFP.

Vietnam's remote northwestern region, which borders both China and Laos, is poor and populated by a patchwork of ethnic minority groups.

There have been previous smuggling cases in the area, which is far from the control of Hanoi.

According to a list of the defendants' names seen by AFP, some of the 89 people were from ethnic minority groups but court officials could not confirm their status.

Facing lethal injection: Judges condemned 30 people to death for their part in trafficking the 12-ton haul

One of the leaders of the four smuggling rings broken up by the police remains at large, state media reported.

Police disrupted the rings in August 2013, making mass arrests and seizing large quantities of illegal drugs.

They also confiscated 20 luxury cars and dozens of guns and other weapons during the raid, state media reported.

Communist Vietnam has some of the world's toughest anti-drug laws.

Anyone found guilty of possessing more than 600 grams (21 ounces) 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.

Thirteen received life in jail and 46 were given either prison terms of up to 20 years, or warnings, the government said in a statement on its Internet site

The 'Golden Triangle' region covering part of Laos, Thailand and Myanmar was formerly one of the world's top producers of opium and heroin but has been overtaken by Afghanistan.

After a two-year hiatus in carrying out capital punishment due to problems procuring chemicals for lethal injections, Vietnam executed its first prisoner by the method last August.

The country currently now has more than 700 prisoners on death row, according to media reports and an AFP tally.

Many have been sentenced for drug offences including dozens of foreigners - although it has been decades since a foreign citizen was executed.

Although Vietnam does not release statistics on executions, rights group Amnesty International recorded 86 new death sentences in 2012 while it said five executions were carried out the previous year.

Amnesty said it was 'dismayed' to learn about the sentences, which come on top of recent death sentences handed out in high-profile corruption and embezzlement cases.

'Amnesty International opposes the death penalty in all cases, without exception,' Rupert Abbott, its researcher on Cambodia, Laos and Vietnam, told AFP.

'Rather than continuing to hand down death sentences, the Vietnamese authorities should be moving towards abolition, in line with the global trend,' he added.

Due to problems with both procuring and producing domestically the chemicals required for lethal injections, some lawmakers have called for a return to executions by firing squad.