South Korea's main opposition People Power Party, claimed that 13 unauthorised IP addresses accessed the internal network of Korea Atomic Energy Research Institute (KAERI) and some of the IP addresses could be traced back to Kimsuky, a North Korean cyber espionage group, reports ZDNet.

According to the US Cybersecurity and Infrastructure Security Agency, Kimsuky is likely tasked by the North Korean regime with a global intelligence-gathering mission.

The group has attacked South Korean facilities in the past too.

South Korea's science ministry said on June 18 that it was investigating a potential hack into a state-run nuclear research institute after its internal network was breached last month.

A Ministry of Science and ICT official said the Korea Atomic Energy Research Institute's network was breached multiple times between May 14-31.

The ministry said the institute has since taken security measures, such as halting its virtual private network and blocking the attacker's internet protocol address.

The science ministry said in a statement that it was currently examining the extent of the hacking incident and the source of the attack.