The comments were similar to other recent pronouncements but were made on Friday at a news conference, an extremely rare occurrence for the commission, the most powerful organ in the North and chaired by leader Kim Jong Il.
It came as international pressure mounted on Pyongyang, and South Korea said the premier of the North's closest ally, China, said his country would "defend no one" once it decides who was responsible for the sinking.
A multinational investigation concluded last week a North Korean submarine fired a torpedo that tore apart and sank the Cheonan in late March, killing 46 sailors in the worst attack on the South Korean military since the Korean War. North Korea has denied responsibility and warned that retaliation or punishment would mean war.
"The South Korean puppet regime's faked sinking of the Cheonan has created a very serious situation on the Korean peninsula, pushing it towards the brink of war," Major General Pak Rim Su, director of the department of policy at the National Defense Commission, told a news conference in Pyongyang, according to broadcaster APTN.
Tensions have soared since South Korea laid out a series of punitive measures and pledged to haul Pyongyang before the UN Security Council. The steps include slashing trade, resuming anti-North Korean propaganda broadcasts across the border and launching large-scale naval exercises off the western coast. US-South Korean military drills are to follow in the coming months.
"These anti-North Korean confrontations are an open declaration of war against us and an extraordinarily criminal act that pushes inter-Korean relations into a state of war," Pak said.
He also said Seoul's resumption of psychological operations near the border was "sharpening possibilities for one-on-one confrontation at an unprecedented speed."
A number of people attended the news conference, including some foreigners who might have been Pyongyang-based diplomats. A uniformed foreign military officer could be seen watching the proceedings, which were aired in full on state television.
In Seoul, Chinese Premier Wen Jiabao told South Korean President Lee Myung-bak his country "will defend no one", once it determines who was responsible for the sinking, the South Korean government said.
While South Korea, the US and Japan have condemned North Korea, China has taken a cautious position.
China's backing would be key to any bid to condemn or sanction North Korea. Beijing, a veto-wielding permanent UN Security Council member, so far has refrained from committing to council action against Pyongyang, its neighbour and traditional ally.
China will decide its stance after considering international probes and the reactions of all countries, Wen told Lee, according to a briefing by presidential adviser Lee Dong-kwan.
Chinese leaders were pressed hard on the issue during talks with US Secretary of State Hillary Clinton and other officials in Beijing earlier this week, and Seoul has already expressed its displeasure over Beijing's hosting the North's reclusive leader Kim Jong Il on a visit just weeks after the sinking.
Wen's pledge not to defend the perpetrators, as reported by South Korea, might also be a sign that Beijing won't exercise its veto at the Security Council. That would likely be conditional on any measures taken against the North being symbolic and unlikely to further destabilise the regime.
Wen and Lee met at the Blue House a day before a three-way summit that will also include Japanese Prime Minister Yukio Hatoyama.
Lee met Wen for 100 minutes, 60 longer than planned, according to Lee, the presidential adviser. The president explained the results of the investigation and gave Wen a Chinese language summary.
Source; SBS News Australia