Five more active players were among those indicted in the southeastern town of Changwon in a further blow to the K-League, according to Yonhap news agency.
A total of 10 players, along with gambling brokers, are alleged to have been part of the match-fixing ring, with eight of the players from a single club.
"Investigations on three more games suspected of match-fixing are going on," Yonhap quoted Gwak Gyu-hong of the prosecutor's office in Changwon as saying.
Officials declined to comment when asked about the case by Reuters.
A midfielder for the team is accused of receiving 120 million won ($110,000) in exchange for helping his side lose a match, Yonhap reported.
Prosecutors believe the player shared money with seven team mates in return for their help in throwing a K-League Cup game.
South Korea's government has promised stiffer punishments for those found guilty of match-fixing, including hefty fines, life-time bans and up to seven years in prison.
State-run sports bookmaker Sports Toto has stopped taking bets on matches at the request of K-League club owners.
The K-League Cup, a relatively minor competition, is thought to be more susceptible to match-rigging as games are held midweek attracting fewer fans and with clubs sometimes fielding weakened teams.
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