The UN Security Council imposed new sanctions against North Korea amid escalating tensions as the North threatened a pre-emptive nuclear strike against the United States.
The council unanimously passed a resolution, agreed by the United States and China, which added new names to the UN sanctions blacklist and tightened restrictions on the North's financial dealings.
North Korea said ahead of the meeting that a new war is "unavoidable" because of South Korean-US military exercises.
The North's military "will exercise the right to a pre-emptive nuclear attack to destroy the strongholds of the aggressors," the foreign ministry said.
North Korea now faces one of the toughest UN sanctions regimes ever imposed after three nuclear tests in 2006, 2009 and the latest on February 12.
And resolution 2094 agreed by the 15-member Security Council threatens "further significant measures" if the North stages a new nuclear test or rocket launch. The resolution expresses "gravest concern" over the nuclear test and adds three new individuals, a government science academy and trading company to the UN blacklist for a travel ban and assets freeze.
The North's foreign ministry warned that adoption of the resolution would fast-track plans to carry out "powerful" countermeasures. It blasted the United States and South Korea over military exercises which have just started in the South.
The North said earlier this week that it would withdraw on Monday from the armistice that halted the 1950-53 Korean War. A foreign ministry spokesman warned a second Korean war is "unavoidable," with the United States and South Korea refusing to cancel their joint military exercise.
"Now that the US is set to light a fuse for a nuclear war, [our] revolutionary armed forces ... will exercise the right to a pre-emptive nuclear attack to destroy the strongholds of the aggressors," the spokesman said in a statement carried by the Korean Central News Agency.
Meanwhile, North Korean television showed a huge military and civilian rally held in Pyongyang's Kim Il Sung square. Senior officials addressing the rally denounced the United States.
There are concerns the current mix of bellicose rhetoric and military drills may spark a random clash with the potential to snowball. Adding to the mix is that relatively new leaders are in charge - Kim Jong Un, supreme leader in the North for just over a year, and South Korean President Park Geun Hye, sworn in only two weeks ago.