Two South Koreans were among 18 people sentenced to death on drug smuggling and trafficking charges in Vietnam, state media said.

The communist country has some of the toughest drug laws in the world, and is notoriously secretive about its executions.

South Korean ex-police officer Kim Soon-sik, 63, and compatriot Kang Seon-hok, 30, were sentenced to death following a four-day trial in Ho Chin Minh City, state media said late Saturday.

Chinese citizen Li Tian Guan, 58, and alleged Vietnamese ringleader Le Ho Vu, 36, were also handed death sentences.

Fourteen other people were also handed death sentences in connection with the case, following the trial in the Family and Juvenile Court, under Ho Chi Minh City People's Court.

The group "illegally stored, trafficked and traded more than 216kg of drugs" between May and June 2020, state media news site Cong an Nhan dan reported.

More than 168 kilograms (370 pounds) of "all kinds of drugs" were confiscated, it reported, without specifying what type.

The narcotics were trafficked from Cambodia to Ho Chin Minh City, according to Vu, where some were "consumed domestically" while others were transported to South Korea, Cong an Nhan dan said.

Officers busted the operation on July 19 in Ho Chin Minh City, according to the reported indictment, when they searched a container truck preparing to complete customs clearance for shipment to South Korea.

Inside they found "40 plastic packages containing white crystals, with a total of 39.5kg of methamphetamine".

State media reported Vu was convicted of "illegal transportation of drugs" and "using fake seals or documents of organisations".

The other 17 people were convicted of "illegal possession of drug", "illegal trading of drugs", "illegal drug trafficking" and "organisation of illegal use of drugs", state media said.

Three defendants were also sentenced to life imprisonment for "illegal drug trafficking", Cong an Nhan dan reported.

It added that one person, who was under 18 years old, was sentenced to 15 years imprisonment.

There was no indication when the executions would be carried out.

Vietnamese courts routinely hand out death sentences for drug convictions, and the country is a leading executioner globally, according to Amnesty International.

More than 100 people were sentenced to death in Vietnam last year, according to the international monitoring NGO the Death Penalty Information Center.

Many face long spells in detention before they are executed, with information about their trials and deaths scarce.

In 2017 Vietnam's courts handed down death sentences to eight drug traffickers for smuggling heroin to China.

Since 2013, Vietnam has carried out death sentences by lethal injection, replacing executions by firing squads.