The crackdown by the National Police Agency for three months to late October rounded up a total of 7,982 sex workers, clients and middlemen, and 35 of them have been arrested, the police said.
The number marks a 31.8 percent rise from those detected in the same period last year, the police said.
Nearly 43 percent were found to have traded sex in new types of sex trade establishments, such as massage shops and kiss parlors, the police said.
About 1,000 out of those detected are accused of selling or arranging sex with underage people, it noted.
As part of the crackdown, the police also shut down 3,463 Internet sites that arrange such trades. In South Korea, prostitution is illegal.
The police are reviewing rules that toughen the punishment on building owners who knowingly lease spaces to those involved in the sex trade and retrieve proceeds earned from the illegal businesses, the police added.