South Korean baseball said Friday it was investigating whether three of its players at the World Baseball Classic "violated behavioural codes" after they admitted drinking.

The Koreans went to Tokyo in early March with high expectations from the baseball-crazy country that they could advance to at least the semi-finals.

However they were eliminated in the preliminary round after losing to Australia and the hosts, with supporters expressing disappointment over the widening gap to rivals Japan, who went on to win the tournament.

South Korean media said that three pitchers had drunk heavily around the time of crucial games and the Korea Baseball Organization launched an investigation.

This week, the three -- Kim Kwang-hyun, a starting pitcher against Japan, Lee Yong-chan and Jeong Cheol-won -- held a press conference and apologised.

The players admitted to going out for drinks on two occasions, one after the 13-4 defeat to Japan.

Irrespective of the apologies, the baseball body is "reviewing whether the three violated behavioural codes expected of the national team in the ongoing probe", a KBO official told AFP. 

Kim's team, SSG Landers, have demoted him to the minor league.

An SSG representative told AFP when and whether Kim will be called back from the minors will "largely depend on the probe outcome".  

At the press conference, the three players expressed their regret.

"I stand here before the media to apologise for my behaviour during the WBC tournament," said Kim, an ace pitcher who has represented South Korea for nearly 20 years.

"I regret my lack of control and carelessness as a veteran," he said during a hastily arranged meeting on Thursday.

Baseball is South Korea's most popular spectator sport.

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