North Korea has walked away from the armistice agreement that ended the Korean War 60 years ago.
"The Chinese are already very fed up. Very, very disappointed, and disappointed far too many times. But they are still not going to do anything about it and the North Koreans know it. North Korea is about the only last true friend that the Chinese Communist Party - in contrast to China - still has in the world and the Chinese Communist Party is not prepared to see the Korean Workers Party collapse. And therefore they can afford to blackmail the Chinese much the same way they are blackmailing South Korea, the US and the rest of the world."
- Steve Tsang, a professor of contemporary Chinese studies at Nottingham University
It also shut down a humanitarian hotline with South Korea, vowing to turn its neighbour into a "sea of fire". North Korean troops were reported to be in a combat mobilisation posture.
Tensions are rising as the US and South Korea are conducting their annual military drills - a move that has provoked the latest threats.
They are also seen as a response to new UN sanctions imposed against North Korea after its nuclear test in February.
The annual US-South Korean military drills are often met with strong rhetoric from the North. They are joint drills known as 'Key Resolve' and they last for two weeks with more than 13,000 troops involved in the exercise.
Since the beginning of this month, another joint exercise known as 'Foal Eagle' - an annual combined field training drill between the two allies - has also been taking place.
North Korea has issued multiple threats to pull out of peace agreements with the South and on Monday, state-run media confirmed the country had pulled out of all of its agreements of non-aggression.
Pyongyang was referring to two agreements made with its Southern neighbour.
"The typical North Korean tactic is to make these outrageous threats ... grabbing the world's attention and then trying to bargain for some kind of concession .... For whatever reason their foreign policy hasn't changed [despite the new North Korean leader]. We have seen the threats before. We can't really end the threats, just make sure they are not carried out. "
- Richard Weitz, a senior felllow at the Hudson Institute
The first is a bilateral pact signed in 1991 that endorses settling disputes peacefully and preventing accidental military flare-ups.
North Korea has also broken the 1953 armistice agreement that brought an end to the Korean War and led to the two countries' current borders and demilitarised zone. It also called for a solution of the 'Korean question', which 60 years later remains far from resolved.
So what does scrapping the armistice agreement mean? With the two sides still technicially at war - could this move lead to an armed conflict? And what role are China and the US playing in the conflict?
Inside Story, with presenter Jane Dutton, discusses with guests: Choi Jong-Kun, an associate professor from the department of political science and international studies at Yonsei University; Richard Weitz, a senior felllow and director for the center for political and military analysis at the Hudson Institute; and Steve Tsang, a professor of contemporary Chinese studies at Nottingham University who is also the director of the China Policy Institute.
"It's an international agreement within a multiple number of states and as long as we keep it valid, the armistice agreement is still valid, regardless .... We have this looming North Korean threat, but at the end of the day South Korea is a very strong state with a very strong military establishment. We are an institutionalised state and regardless of the [current] institutional transition, South Korea is responding to the North Korean threat very proportionally. So every time North Korea is trying to escalate, we are trying to keep it very calm. But this is democracy so we have many media outlets trying to make a lot of noise and buzz out of this North Korean threat."
- Choi Jong-Kun, an associate professor at Yonsei University