"The two-day drill is under way through simulators to ensure the safety of our nuclear power plants under cyberattacks," a spokesman from state operator Korea Hydro and Nuclear Power Co. (KHNP) told the agency.
The tests are being carried out at the company's four nuclear power facilities, which house 23 nuclear reactors and produce a third of the country's electricity. The announcement of the safety drills comes after a series of leaks this month of classified information about the reactors, made it into social networking websites.
South Korean officials sought to allay fears that the safety of the reactors could be compromised. "It is 100 percent impossible that a hacker can stop nuclear power plants by attacking them, because the control monitoring system is totally independent and closed," a KHNP official told Reuters. South Korean authorities are investigating the hack, but have so far not commented on who they believe to be behind the attack.