The Swedish spy, who is a member of Sweden's coaching staff, said he later set up a telescope and spied on the team from a local couple's home.
Sweden, competing at their first World Cup since 2006 after knocking out Italy in the playoffs started the game with real attacking vigour and intent as they looked to start Russian Federation 2018 on the front foot.
Swedish media reported that a Swedish staffer rented a house in Austria near the South Korean training ground with the intention of viewing the Koreans' drills in the buildup to the World Cup in Russian Federation.
Mexico, who top the group on three points alongside Sweden, are next up for South Korea on Saturday in Rostov.
South Korea hope to have kept their tactics against Sweden a surprise by swapping shirt numbers in recent training sessions and matches, coach Shin Tae-yong has said.
"We switched them around because we didn't want to show our opponents everything and to try and confuse them", said Shin.More news: Audi CEO Rupert Stadler arrested
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The scout had previously tried - and failed - to convince the South Koreans to let him witness a training session by convincing them that he was a tourist.
Swedish coach Janne Andersson apologized to the South Korean team Sunday for an incident in which a Swedish scout was caught looking in on a South Korean practice in Austria.
"It's very important that we show respect for opponents", Andersson said.
"It's very hard for Westeners to distinguish between Asians, and that's why we did that".
"It took a long vehicle journey up the mountains to reach the house, but it was a ideal spot to observe the Korean team's training", Lars Jacobsson, a member of the Swedish coaching staff, said on Sunday.
"All coaches probably feel their opponents are always spying on them".
South Korea's only real chance to equalise came in the 92nd minute, when Hwang Hee-Chan's headed attempt went wide to the left. "I think it's perfectly natural that we all try to get as much information on each other as we can". Sweden had 15 shots, five on frame, while holding South Korea to zero shots on goal.