South Korea's coach Shin Tae-yong says he deliberately made his team wear different numbered shirts in recent friendlies to confuse World Cup opponents.
He said all but star player Heung-Min Son and captain Ki Sung-yueng were given different shirts in games against Bolivia and Senegal in Austria earlier this month to outwit anyone checking up on his team.
The claim came just 24 hours before his side open their World Cup campaign against Sweden, an encounter which has been spiced up by claims of spying as well as the Korean coach's shirt subterfuge.
In his press conference, Swedish coach Janne Andersson was forced to apologise after it was claimed one of his scouts had been caught spying on Monday's opponents at a closed training session in Austria.
But the claim by his Korean opposite number added an extra layer of intrigue to the Group F clash.
"All of the others played in numbers a little bit confusing, that's why we switched the numbers," Shin Tae-yong said.
"It's very difficult for Westerners to distinguish between Asians, that's why we did that."
Asked about claims that Sweden had spied on his team, Shin Tae-yong was calm, saying: "I don't think that's bad", adding that all teams needed to know about their opponents.
There have been counter-claims that the Koreans also spied on the Swedes in the run-up to Russia.
The row centres on Swedish scout Lasse Jacobsson who reportedly covertly watching the Koreans prepare for the World Cup.
Jacobsson had apparently rented a house in the town of Leogang, near Salzburg to 'spy' on Sweden's first opponents.
"He heard about a practice session, he didn't understand that it was a closed session, he didn't understand and he watched from a distance," said Andersson, attempting to downplay the incident.
"It's very important we show respect to all our opponents in all circumstances, if someone could interpret it in another way we regret it.
"It's been made a mountain out of a molehill."