A police investigation pointed to North Korean hackers after emails sent by the same IP address contained malware.
Police investigations have pointed to North Korea as responsible for recent attempts to hack South Korea's virtual currency exchanges, a report said Wednesday.
They reached the conclusion after investigating cyberattacks on dozens of email accounts of employees at four local bitcoin exchanges, Yonhap news agency said.
North Korea is heavily sanctioned by the United Nations for its nuclear and missile programmes and speculation has been mounting that the cash-strapped regime is turning to digital currency to obtain funds.
Police said the North Korean hackers, pretending to be security authorities, sent emails containing malware between July and August this year, according to Yonhap.
The emails were sent from the same IP address linked to previous North Korean hacking attempts against Seoul, police were quoted as saying.
The test emails sent before the actual attack were traced back to the North, the report said.
No computers were compromised and no digital currency was stolen in any of the cases, the report said. Police could not be reached for comment.
South Korea is one of the world's busiest trading hubs for cryptocurrencies, with Seoul-based Bithumb ranking as the world's largest exchange for the ethereum virtual currency.
A report by security researcher FireEye earlier this month said North Korean hackers had launched attacks on at least three South Korean cryptocurrency exchanges since May.
The hackers were using "spearphishing" attacks, it said, targeting the personal email accounts of employees at the exchanges.
"It should be no surprise that cryptocurrencies, as an emerging asset class, are becoming a target of interest by a regime that operates in many ways like a criminal enterprise," it said.