Sixty-four South Koreans who had been detained in Cambodia for alleged involvement in cyberscam operations returned home Saturday and were under arrest, a police official told AFP.

South Korea had sent a team to Cambodia on Wednesday to discuss cases of fake jobs and scam centres involved in kidnapping dozens of its nationals.

"A total of 64 nationals just arrived at the Incheon International Airport on a chartered flight," the official said.

Seoul had said around 60 South Koreans had been detained by authorities in Cambodia over the alleged crimes, and vowed to bring them home.

The repatriation follows a public outcry in South Korea over the torture and killing of a Korean college student in Cambodia this year, reportedly by a crime ring.

The individuals were arrested on board the chartered flight shortly after boarding, the official said.

All 64 have been taken into custody as criminal suspects upon arrival at the Incheon airport and will be transferred to the police stations with jurisdiction over their respective cases, the official said.

The suspects, many wearing masks and caps, were led into the airport's arrival hall by two police officers each, their arms firmly linked on either side, TV footage showed.

Most of them appeared to be handcuffed, with pieces of cloth covering their restraints.

The repatriated individuals are implicated in various crimes linked to voice phishing, romance scams and so-called "no-show" fraud schemes, Park Sung-joo, head of the National Office of Investigation, told reporters at the airport.

There have been suspicions of drug use in Cambodia, he added, "so all of those returned will undergo drug testing as a standard procedure".

National Security Adviser Wi Sung-lac previously said the detained individuals included both "voluntary and involuntary participants" in scam operations.

Vice foreign minister Kim Jina thanked Cambodian authorities, adding Seoul confirmed Phnom Penh's "ongoing efforts to crack down on such criminal activities and commitment to close cooperation with our country".

Seoul has said about 1,000 South Koreans were estimated to be among a total of around 200,000 people working in scam operations in Cambodia.

Some are forced under threat of violence to execute "pig butchering" scams -- cryptocurrency investment schemes that build trust with victims over time before stealing their funds.

The multibillion-dollar illicit industry has ballooned in Cambodia in recent years, with thousands of people perpetrating online scams, some willingly and others forced by the organised criminal groups running the fraud networks, experts say.

- Torture and human trafficking -

Amnesty International says abuses in Cambodia's scam centres are happening on a "mass scale".

There are at least 53 scam compounds in the country where organised criminal groups carry out human trafficking, forced labour, torture, deprivation of liberty and slavery, according to the rights group.

Cambodia's anti-cybercrime commission said in a statement on Wednesday that authorities had arrested 3,455 online fraud suspects nationwide from 20 Asian and African countries since late June.

Authorities sent dozens of suspected "ringleaders and their accomplices" to court in 10 of the cases involving online fraud, murder and human trafficking, according to the statement.

More than 2,800 foreign nationals were deported from Cambodia, and authorities "rescued some victims from trafficking", it said.

South Korean police have said they would also conduct a joint investigation into the recent death of a college student in Cambodia, a case that shocked South Koreans.

The student, reportedly kidnapped and tortured by a crime ring, was found dead in a pickup truck on August 8.

An autopsy revealed he "died as a result of severe torture, with multiple bruises and injuries across his body", according to a Cambodian court statement.

South Korean and Vietnamese authorities are also conducting investigations after a Korean woman was found dead on October 8 near the Vietnam-Cambodia border, according to Seoul's foreign ministry.