South Korea's state-run electricity distributor issued a power shortage alert Friday due to a surge in electricity consumption caused by cold temperatures.

The Korea Power Exchange issued the "watch" warning, the fourth-highest level, at 11:25 a.m. as the country's electricity reserve dropped below 4 million kilowatts for more than 20 minutes.

The company's "attention," the third-highest level, comes when the reserve level drops to between 2 million and 3 million kilowatts. The second-highest warning of "caution" is issued when the reserves fall to less than 2 million kilowatts.

A temporary blackout that affected about 2 million households in September 2011 caused billions of won in damages and a 61-billion-won damage suit against the government despite its small scale compared to a nationwide blackout.

Some nuclear reactors in South Korea have been shut down for safety inspection or have recently reported malfunctions, raising concerns that the country may suffer a power shortage during winter.

The latest surge in energy consumption has largely been caused by unusually cold weather for this early into winter.

Freezing weather and heavy snow have gripped South Korea, bursting water meters and disrupting transportation. The mercury dropped to minus 10.3 degrees Celsius in the capital on Thursday, the lowest temperature this winter, and temperatures are expected to remain below zero in most parts of the country for the weekend.