The worth of the two illegal operations is said to be around KRW900bn ($797m), according to The Korea Herald.
The authorities said 17 people who were using the illegal gambling sites were also apprehended for violating the National Sports Promotion Act. Arrests were made after police raided the offices of two sites and the residences of the suspected operators.
Authorities seized cash and real estate worth KRW8.12bn, including KRW1.95bn in cash, three apartments and two detached houses. The police stated these properties were bought using illegally gained funds.
One of the main culprits was said to have fled the country and is currently on Interpol's most-wanted list.
The man allegedly operated an illegal sports gambling site in South Korea from March 2016 and his operation is worth around KRW900bn, with 3,300 members and servers also in Vietnam and China.
The culprit is suspected to have illegally profited from member management, currency exchange, bulletin board management and similar activities. He additionally helped establish another illegal gambling site in June 2018; the new site is worth KRW100bn and has around 1,800 members.
Recently, three people were arrested in the Philippines and deported back to South Korea. They were suspected of running an illegal online gambling operation and were on wanted lists since 2019.
The only legal forms of gambling in South Korea are lotteries, horse racing, boat racing and cycling. Casinos, however, are prohibited and mostly reserved for foreigners only, with local nationals facing jail time for playing in a tourist-aimed casino.
Citizens are even encouraged not to engage in gambling while abroad.