SEOUL -- South Korea saw crimes of supplying illegal psychoactive drugs increase by over 33 percent in the first half of this year from a year ago as an increasing number of foreigners used the country as a route to circulate illegal drugs, prosecutors said Sunday.

The Supreme Prosecutors' Office said they caught 4,601 people using or circulating locally banned psychoactive drugs, including methamphetamines and marijuana, in the first six months of this year. The number marks a 4.8 percent increase from the same period last year.

Among the total, those caught for illegal drug use accounted for 50.6 percent while the rest was convicted of circulating, smuggling or producing illegal drugs, the prosecution said.

It said those who were convicted of circulating, smuggling or producing drugs amounted to a total of 1,704 in the first half, marking an increase of 33.4 percent from a year earlier. Those convicted of drug use fell 9 percent year-on-year.

The sharp increase in the illegal drug supply is attributable to foreign drug rings, mostly from China, Southeast Asian nations and Nigeria, who are attempting to use South Korea as a route to move their products, the prosecution said.

"An increasing number of global drug smugglers from Nigeria and Southeast Asian countries are trying to use South Korea as a passage in order to avoid tight screening in their destination countries like Japan or the United States, the biggest drug consumers," a prosecution official said.

Amid the increased illegal drug supply, the prosecution confiscated a total of 30.6 kilograms of illegal drugs in the first half, compared with 24.6 kg a year earlier. Methamphetamines accounted for two-thirds of the drugs that were confiscated this year, it said. (Yonhap news)