AFP - North Korea Friday threatened fresh steps to defend itself if world powers impose sanctions over its nuclear test, but the United States said it had enough troops in South Korea to protect its key ally.
Tensions have been running high since Kim Jong-Il's regime tested a nuclear bomb on Monday for the second time and warned it could launch an attack on the South, renouncing the armistice that ended the Korean War in 1953.
Defying international condemnation of its nuclear arms programme, the reclusive communist state vowed Friday to respond to any fresh sanctions imposed by the United Nations.
"If the UN Security Council provokes us, our additional self-defence measures will be inevitable," the North's foreign ministry said in a statement carried by official media.
"Any hostile acts by the UN Security Council (UNSC) will be tantamount to the demolition of the armistice," the ministry said in reference to the truce which ended fighting in the 1950-53 Korean War.
"The world will soon witness how our army and people stand up against oppression and despotism by the UNSC and uphold their dignity and independence."
The Council has been negotiating a response to the North's latest nuclear test, expected to be a resolution condemning the move. But it was not yet clear if that would include new sanctions on North Korea.
"This is quite a complicated discussion," Britain's UN ambassador John Sawers said after the latest round of talks on Thursday. "We need some time."
Russia has said it opposes punishing Pyongyang "for the sake of punishment alone" while China -- another veto-wielding member of the Security Council -- is wary of a possible influx of refugees if the North Korean regime collapses.
South Korea and the United States put their troops on the Korean peninsula on higher alert on Thursday, and Seoul's defence ministry said forces were keeping a close watch on the land and sea border with the North.
US Defence Secretary Robert Gates, en route to a regional security meeting in Singapore, accused the North of "very provocative, aggressive" actions.
But Gates said he was unaware of any unusual troop movements in the North, which has around 1.1 million soldiers, compared with a total of 708,500 South Korean and US troops south of the border.
"I don't think there is a need for us to reinforce our military presence in the South. Should the North Koreans do something extremely provocative militarily, then we have the forces to deal with it," he added.
In a sign of possible trouble ahead, Chinese fishing boats were leaving the tense border area in the Yellow Sea, with the number of vessels more than halving on Thursday, South Korea's defence ministry said.
"As this could be a signal foreboding a possible provocation by the North, we are watching the situation closely," ministry spokesman Won Tae-Jae said, adding that the move might also be unrelated to military tensions.
Despite the increased tensions, hundreds of South Korean workers travelled to the North Friday to work at a joint industrial complex, and commercial ships from the North were sailing south of the border, Yonhap news agency reported.
Pyongyang warned Wednesday that it might attack US or South Korean ships after the South said it was joining a US-led international effort to stop the trade in weapons of mass destruction.
The North has been an active exporter of missiles in recent years, but it is not known if any of its ships have been boarded and searched since the programme began in 2003.
After the Security Council censured its April 5 rocket launch and tightened existing sanctions, the North said it was quitting the disarmament talks and would restart its Yongbyon atomic facility.
Many experts believe, however, that the North is not yet able to deliver a nuclear weapon by missile.