Reliant entirely on imports for meeting energy requirements that feed some of the world's biggest companies such as Hyundai Motor Co. and Samsung Electronics, South Korea activated the drill late on Monday.

It involves keeping staff on high alert and preparing to cope with any damage to facilities. 

Security concerns over North Korea, which in 2010 shelled civilians on a South Korean island and is accused of sinking one of the south's warships earlier that year, were heightened after Seoul said the North had test fired a short range missile shortly before the announcement of Kim's death.

"We, since Kim Jong Il's death, have been holding a daily internal meeting reviewing risk management," a spokesman at state-run Korea Gas Corp., the world's largest corporate buyer of liquefied natural gas (LNG), told Reuters.  

"We are intensifying security over our gas facilities and have an emergency team in place." 

The world's fifth-largest crude importer and the second-largest LNG buyer after Japan currently holds 120 million barrels of oil in reserve, or 82 percent of capacity, a spokesman at state-run Korea National Oil Corp. (KNOC) told Reuters on Tuesday.

Crude accounts for 90 percent and the remainder is products. The storage is equivalent to over 90 days of the country's consumption, the spokesman said.

"Chances of supply disruption rise along with increasing geopolitical risks," Brandon Lee, senior energy analyst at Macquarie Securities Korea, said. "Building stocks, for which the government has made a lot of effort, offer limited help and is not a fundamental solution."

The country has 3.42 million tons of LNG in storage, 92 percent of capacity and enough to cover demand until the end of February, the Ministry of Knowledge Economy said in a statement on Monday.

KNOC has put its nine onshore and offshore oil reserve sites on high alert. Korea Electric Power Corp. (KEPCO), a state-run utility, said in a statement that it has activated an emergency work system to ensure security of power supply facilities.

The nation is currently operating 19 nuclear power plants out of a total of 21, according to government data. While there is no latest information available, official data published in September showed that more than 30 percent of power supply was  from nuclear generation in 2010. 
     
South Korea's state-run and private oil and gas firms, including utilities and refiners, have not moved to boost imports, release stocks or raise refinery runs, government and industry officials said.

Apart from being on high alert, most refiners are opting to maintain business-as-usual operations. In talks for March crude imports, some are considering lowering imports compared with a year ago due to weak processing profits.

Of the total oil in reserves held via KNOC, South Korea directly owns 80 million barrels. Foreign companies have built the remaining inventory as KNOC leases part of the facility. The country has a right over those barrels in an emergency.

Any plan or request to release oil from its reserve would happen only if supplies are disrupted, the KNOC spokesman said.

The last time KNOC released oil from South Korea's strategic reserves was in July and August, when nearly 3.5 million barrels of crude and refined products were issued under a coordinated plan by the International Energy Agency (IEA).