The consolidated defence command, a meeting of some 200 top military and government officials presided over by Prime Minister Han Myeong-Sook, said it would step up its 24-hour monitoring of nuclear facilities.

"The command has decided to beef up military countermeasures in parallel with the ongoing efforts to dismantle North Korea's nuclar programmes," the Joint Chiefs of Staff said in a statement.

"It will step up the around-the-clock monitoring and surveillance over North Korea's nuclear facilities... (and) beef up the response forces at an early date."

The joint chiefs said regional instability had increased following North Korea's nuclear test and missile launches "as countries in the region continue with building up military capability."

South Korean officials were criticised for insufficient advance knowledge and slow verification of the nuclear test last October.

The defence ministry last month warned that North Korea's nuclear and conventional weapons pose a serious threat to the South.

The ministry, in a biennial White Paper, said the communist state produced an estimated 30 kilograms (66 pounds) of plutonium over the past three years -- enough to make up to five atomic bombs.

The North had also acquired some 200 artillery pieces which could strike Seoul when sited along the border, and about 40 percent of its 820 fighter jets were just north of the frontier.

The hardline communist North and capitalist South have remained technically at war since the 1950-53 conflict, which began with an invasion by the North.

Some 680,000 South Korean troops, backed by 29,500 US soldiers, are confronting the potential threat from the North's 1.1 million-strong military.

Six-nation talks on dismantling North Korea's nuclear programme are expected to resume early next month in Beijing.

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