Seoul: South Korean President Park Geun-hye said on Tuesday the leak of data from the country`s nuclear operator was a "grave situation" that was unacceptable as a matter of national security.
"Nuclear power plants are first-class security installations that directly impacts the safety of the people," Park said at a cabinet meeting, according to her office.
"A grave situation that is unacceptable has developed when there should have been not a trace of lapse as a matter of national security," she said.
Earlier, a South Korean official said Seoul had not ruled out the possible involvement of North Korea in the cyberattack on South Korea`s nuclear power plant operator, although Park did not make any mention of it.