Gwangju Police said Monday it has apprehended 12 foreigners, including illegal immigrants, on suspicion of using narcotic substances at a local foreigner-only karaoke, known locally as "noraebang."

The suspects, whose identities were withheld, are suspected of taking ketamine inside a noraebang in Usan-dong, Gwangju, according to the Gwangju Metropolitan Police Agency's drug investigations unit. The majority of the suspects were Vietnamese nationals who had gathered for a birthday party when they were taken in by police.

Officials raided the scene on a tip-off that an employee of the establishment was taking illegal drugs. A total of 39 foreigners were on the premises at the time, 30 of whom were illegal immigrants.

Rapid drug tests confirmed that two of the noraebang employees had used drugs.

Police plan to request an arrest warrant for 10 of the suspects, and plan to hand over the rest of the illegal immigrants to the Korea Immigration Office.

South Korean law bans drug use, transaction possession or distribution for any South Korean or of anyone inside its territory, including individuals from countries that legalize use of such drugs. The Narcotics Control Act stipulates using banned substances is punishable by up to five years in prison.

The rise of drug-related crimes is a growing issue in South Korea, which punishes use, possession or distribution of even "soft drugs" like marijuana and once touted itself as a "drug-free" country.

From January to September of this year, 20,230 people were caught by police for drug-related crimes, a 47.6 percent increase from the same period the year before and even more than 18,395 for the entire 2022, according to the monthly report by the Supreme Prosecutors' Office.

The number of foreigners charged with drug-related offences more than doubled in the last five years, from 948 in 2018 to 2,294 from January to September of this year.