North Korea says it is ending all non-aggression pacts with South Korea in retaliation for a new round of United Nations sanctions imposed following Pyongyang's third nuclear test.
The latest sanctions - approved unanimously - seek to block all avenues of funding for Pyongyang's nuclear programme.
North Korean diplomats, cash transfers and access to luxury goods are the targets. Asset freezes and travel bans are imposed on three individuals and two firms linked to North Korea's military, the BBC reports.
In a 15-0 vote, the council on Thursday backed Resolution 2094 imposing the fourth set of sanctions against North Korea following earlier nuclear tests and a long-range missile launch on 12 February this year.
North Korea's threats are becoming shriller as its isolation continues.
Having threatened to launch a pre-emptive nuclear strike against the United States and withdraw from South Korea's 60-year-old armistice agreement, Pyongyang now says it is ending all non-aggression pacts with the South.
It is also shutting down communications at the main crossing point between the two countries.
Inside North Korea, meanwhile, its leaders are building up the sense of crisis, with reports of camoflague netting on public transport, visits by the leader to frontline units and a big rally in the capital, the BBC reports.
Its foreign ministry has warned that a second Korean war is "unavoidable," with both the US and South Korea refusing Pyongyang's demands to cancel a large-scale joint military exercise, due to start on Monday.
After Thursday's vote, America's ambassador to the UN Susan Rice said the sanctions would "further constrain" North Korea's ability to develop its nuclear programme and warned the UN would "take further significant actions" if Pyongyang were to carry out another test.
China's UN ambassador Li Baodong said that "the top priority now is to defuse the tensions" on the Korean peninsula and the six-party talks on the North's nuclear programme must resume.