South Korea may be forced to take extreme measures to avoid a nationwide blackout Monday with six nuclear reactors still out of work for maintenance, the government said.

The Ministry of Trade, Industry and Energy earlier said the country's power reserve was expected to drop to as low as 1.8 million kilowatts during the peak hours of 2-5 p.m., far below what is considered a safe level of 4 million kilowatts.

Conditions worsened after a 500,000-kw generator at a thermal power plant in Dangjin halted its operation earlier in the day due to technical problems.

Officials at the Dangjin power plant said they will not be able to restart the generator at least until next week.

Energy Minister Yoon Sang-jick said on Sunday that even minor problems at any of the country's power plants this week could lead to serious consequences, including blackouts, noting the country's electricity consumption was expected to reach its annual peak in the first three days of the week.

The country has been struggling daily to keep its power reserve at a safe level since it was forced to shut down two nuclear reactors for substandard parts used under fake quality certificates years earlier.

Seven other reactors, each generating up to 1 million kilowatts of electricity, had also been out of operation for inspection or scheduled maintenance though three of them have since been put back to work. (Yonhap News)