SOUTH Korean footballers were left dumbfounded at an international tournament in Indonesia when organisers played North Korea’s anthem instead.

Ahead of an AFC under-19 Championship qualifier against Jordan at the Patriot Candrabhaga Stadium on the outskirts of Jakarta, the South’s team lined up with their hands on their hearts.

But instead of Seoul’s hymn-like anthem Aegukga, North Korea’s national tune blared out, leaving them stony-faced and silent.

The South’s coaching staff told officials of the mistake, and while the correct song was then played, they protested after the game.

Seoul’s football authorities said Tuesday they will file a formal complaint with the Asian Football Confederation (AFC).

“This is the first time that the North Korean anthem was played instead of Aegukga at any official international match for any level of the national football team,” the Korea Football Association said in a statement.

The tournament’s local organising committee blamed the error on the audio operator in charge of playing the anthem.

“During the rehearsal, the South Korean anthem was played. But somehow the operator later picked the wrong song file,” Gatot Widagdo, media co-ordinator for the AFF U-19 Youth Championship, told AFP on Tuesday.

“The operator has (since) been replaced and we have apologised to South Korea verbally and in writing.”

The North’s anthem was “stopped immediately”, the AFC said.

“An investigation into the mistake has been held,” it said in a statement Tuesday.

“The AFC apologises to the Korea Republic team and the Korea Football Association and the AFC will take the appropriate steps to ensure this error cannot be repeated.”

The mistake comes as a rapid diplomatic thaw takes hold on the peninsula, led by South Korea’s dovish President Moon Jae-in who has met with the North’s Kim Jong-un three times this year.

North and South Korea formed unified teams for some events at the Asian Games two months ago, also hosted by Indonesia, and reached the women’s basketball final.

But the democratic South remains technically at war with the communist North after the 1950-53 Korean War ended with an armistice instead of a peace treaty.

It is not the first time sports organisers have been stumped by Korean politics.

At the 2012 Olympics, North Korea’s women footballers walked off the pitch ahead of a group match in Glasgow when they were introduced next to images of the South Korean flag.