SEOUL—South Korean prosecutors have busted an online gambling ring operated by Koreans from Manila which cleared some $100 million over 18 months, officials said Tuesday.

The Seoul Central Prosecutors' Office said four South Koreans have been charged. Two others have fled abroad but prosecutors will seek to have them extradited.

Online gambling is illegal in South Korea and regular gambling is strictly limited, with only one casino in Korea open to locals.

The ring allegedly opened a casino in Manila in February last year. They hired 30 Filipino dealers and webcast baccarat games being staged at the casino to domestic on-line participants.

In order to assure on-line gamblers they were taking part in real-time games, the ring depicted CNN broadcasts in its on-line coverage.

Some online gamblers wired more than $100,000 for a single bet.

The suspects allegedly earned $100 million over 18 months until their operation was busted in August, the prosecutors added.