Australia upset South Korea 8-7 in their opener at the World Baseball Classic(WBC) tournament in Tokyo on Thursday.

Starting pitcher Ko Young-pyo allowed two runs on four hits with four strikeouts in four-and-a-third innings as the 2009 WBC runners-up struggled against the Australians.

Robbie Perkins and Robbie Glendinning both hit homeruns with three runners on for Australia, while Yang Eui-ji batted a three-run home run for Korea.

Team Korea will hope to improve its chances of progressing past the group stage when it faces two-time champions Japan on Friday.

The top two teams from Pool B comprising South Korea, Japan, Australia, China and the Czech Republic will advance to the single-elimination bracket with the top two from the other three pools.