South Korea on Thursday held a nationwide drill aimed at enhancing preparedness for potential blackouts as this winter's unprecedented cold wave has driven up electricity demand.

The 20-minute exercise was carried out under a scenario where the country's electricity reserves fell below two million kilowatts, and simulated responses to possible emergency situation.

As the drill began at 10 a.m. local time with the sound of siren, people were asked voluntarily to take part in an energy- saving campaign by turning off lights and appliances at homes and offices.

Public buildings were advised to rely on emergency generators that can produce at least five million kilowatts of electricity during the training.

Traffic lights were switched off at 18 intersections nationwide, while facilities vulnerable to blackouts, such as elevators, subway stations and hospitals, carried out separate emergency rescue operations, according to a statement from the Ministry of Knowledge Economy.

South Korea's electricity reserves have fallen below the stable level of four million kilowatts six times this winter, forcing the Korea Power Exchange to issue preliminary warnings for a power shortage.

The country conducted a similar drill in June.