A US blockchain analytics firm says North Korean hackers recently moved 21.9 million dollars' worth of stolen cryptocurrency to a Russian-based exchange to launder illicit crypto assets.

Chainalysis says the amount is believed to be part of the cryptocurrency stolen from US companies last year. It says the alliance between North Korea and Russia in cyberspace presents a security threat.

A United Nations expert panel says state-affiliated North Korean hackers have stolen huge amounts of cryptocurrency, and that the proceeds could be used to finance nuclear and missile programs.

Chainalysis believes the North has been moving the stolen cryptocurrency to exchanges in Russia because it's "the safest place" to avoid detection as Western nations tighten sanctions on the North.

The firm estimates that this year alone, North Korea has already stolen over 340 million dollars in cryptocurrency.

In an interview with NHK, Chainalysis CEO Michael Gronager said that "what we see today is a Russia that's already sanctioned" economically, and which therefore has nothing to lose by working with North Korea.

He said the relationship has become stronger as a result, raising serious concerns.

Gronager said it's vital that governments improve their ability to stop money laundering and confiscate crypto assets stolen through hacking.