North Korea again denied its involvement in a series of data leaks at South Korea's nuclear power operator and rebutted Seoul's interim probe results that accused the communist regime of conducting the hacking attacks.

The North's Central Internet Research Institute said that the investigation that linked Internet protocol addresses used in the attack to North Korea is groundless and was fabricated by Seoul, according to Pyongyang's state media Korean Central News Agency.

The denial follows a March 17 announcement by a special investigation team that found the data leaks at the Korea Hydro and Nuclear Power Co. "believed to have been caused by an (unidentified) group of North Koreans hackers."

In December, an unidentified hacker, claiming to be an activist against nuclear power, had posted data about nuclear power plants, including their blueprints, five times and threatened to destroy the facilities while demanding they be shut down.

Earlier this month, the hacker renewed its threats by posting more files on Twitter that included documents concerning the country's indigenous advanced power reactor 1400, while demanding money in exchange for not handing over sensitive information to third countries.

The state-run KHNP operates 23 nuclear reactors in South Korea that provide nearly one-third of the country's energy demand. (Yonhap)