The same methods including raised and dented printing and no-smudge inks that are normally used for real banknotes have been applied to the newly found supernote, he said.

“You need facilities worth some $100 million to produce counterfeit bills of this quality and no crime rings would invest that much to make fake dollars,” he said.

“Only state-level organisations can afford such facilities.”

South Korean news media suggested the North might have resumed producing fake banknotes to circumvent tightening international sanctions against its nuclear and missile development.

But Yi said there was no evidence to link the newly found supernote to North Korea — although Pyongyang has a track record of its diplomats getting caught with high-quality forgeries.

The bank has alerted judicial and intelligence authorities about the discovery, Yi added.