Former South Korean Olympic wrestling champion Kim Hyeon-woo bowed out of the first round at the Rio de Janeiro Olympics on Sunday.

Kim, who won the 2012 gold medal in 66kg Greco-Roman, lost 7-5 to Roman Vlasov of Russia in the round of 16 in the 75kg event.

Vlasov is the 2015 world champion and the reigning gold medalist in the 75kg weight category. Kim was trying to become the second South Korean wrestler to win two straight gold medals in two different weight classes.

Kim and Vlasov are two of the best in their class and were expected to battle for gold here. But there are no seeds in Olympic wrestling and a random draw for the single elimination bracket pit the two against each other from the start.

Kim went up 2-0 with a shoulder throw, but Vlasov scored six quick points by executing successive moves.

Kim got a point back with 57 seconds remaining. Then with five seconds remaining, he pulled off a grand amplitude throw.

The move is worth four points if the turn is executed without the opponent's body the touching the mat. Kim's coach, An Han-bong, thought the South Korean should have received four points, and An challenged the ruling when the referee awarded Kim just two points.

After a video review, the referee upheld the original decision.

And because Kim lost the challenge, Vlasov received one extra point, giving him a 7-5 victory.

South Korea plans to appeal the ruling.

In the other Greco-Roman event Sunday, Lee Jeong-baik lost to Stig Andre Berge of Norway 2-0 in his first match.

Lee barely put on any moves at all over his six minutes of action and gave up two technical points in the loss.

"I just didn't have it today," Lee said. "I was nervous since this was my first Olympics. I should've overcome that but I couldn't." (Yonhap)