External lights on bridges, commercial and residential blocks and other big buildings must be switched off after midnight along with advertisement and store signs, the Ministry of Knowledge Economy said in a statement.

Entertainment businesses would have to switch off outdoor signs after 2 a.m. and petrol stations would be asked not to use lights during the day.

After a seven-day grace period, offenders will be liable to a fine of up to three million won ($2,700).

The ministry also said it is asking public employees to keep their cars at home at least once a week.

"The measure will limit the non-essential use of energy to an extent that minimises inconvenience to businesses and the public," its statement said.

The ministry upgraded its energy alert after the price of benchmark Dubai crude oil stayedover $100 per barrel for five consecutive days.

Crude prices have seen big rises over the past few weeks as protests flared across the oil-rich Middle East and North Africa, with the Libyan regime clinging to power while leaders in Tunisia and Egypt have already been toppled.

South Korea, Asia's fourth largest economy, relies on imported oil needs.

It was the world's fifth-largest importer last year when it brought in 872 million barrels of crude 82 percent from the Middle East.

The oil price rise is hampering efforts to curb inflation, which reached an annual rate of 4.1 percent in January.