The number of drug arrests made against foreign nationals in South Korea has increased much faster than the foreign population, a study has found, with the nature of the offenses also becoming more serious.

According to a study by the Criminal Investigation Institute, a research center at the Korean National Police University, the number of drug arrests made against foreigners reached 2,335 in 2021, up from 359 cases in 2012.

That is a 6.5-fold increase, while the foreign population rose just 35 percent over the same period. Separate statistics made available by police show the incidence of drug crime has roughly doubled among the general population in that time.

The nationalities of those involved in drug crimes have also become more diverse, the study showed. According to the study individuals of 71 different nationalities were implicated in drug cases last year, compared to 31 nationalities in 2012.

The study also showed that a greater number of offences involve smuggling. In 2021, trafficking cases accounted for 20.5 percent of all narcotics cases involving foreign nationals, while the figure stood at 5.8 percent in 2012. Conversely, drug use accounted for just 44.7 percent of cases last year, down from 61.8 percent in 2012.

Drug-related crimes have come into the spotlight in recent weeks, thanks to a high profile case involving a local celebrity.

Last month, the Busan Metropolitan Police Agency took 72 foreign nationals into custody in connection with drug trafficking. The police agency said they sold the drugs, ketamine and ecstasy, at parties arranged on social media.

On Oct. 5, the South Chungcheong Province Police Agency said it had rounded up some 40 foreign nationals on suspicion of trafficking and selling methamphetamine. The group smuggled the drug in from Laos using international mail, the police agency said.

The series of drug cases in recent weeks have fanned criticism that drug laws are not being properly enforced.

Illegal drug use can lead to a prison sentence of up to 10 years or a fine of up to 100 million won. Those involved in producing or smuggling drugs face prison terms more than five years, up to life in prison.

But courts have been imposing much smaller fines and jail terms. Last year, drug offenders in 2,089 cases received suspended sentences, accounting for 44 percent of 4,747 first-trial convictions.

Only 20 cases resulted in prison sentences longer than 10 years.

Prosecutors have also pressed charges in a relatively low proportion of cases.

In 2021, prosecutors made indictments in only 6,205 of the 18,695 drug crime cases they reviewed. Indictment was suspended for 3,668 cases, while 315 cases were summarily indicted.

The rate of indictments for drug suspects is similar to the rate for overall crimes, but the overall rate includes lighter offences that generally have lower rates of indictment.