Yes, the actions invoked by the North Korean government makes it glaringly obvious that North Korea is trying to break the sanctions put forth by the UN. There are certain rules and regulations that the North Korea government must follow and abide by, and their recent actions are in my opinion direct violation of the UN sanctions.
I don't think anyone takes North Korea seriously. Whether they should or not, I don't know, but threats don't work, they just tend to infuriate. I think North Korean government needs to play up to their national persona of defenders against the inevitable evil threat; South Korea and the USA. China is even backing off support, yet S. Korea keeps evoking nuclear war something that the world community will not tolerate. So, unless they are absolutely ignorant, they've gone the worst possible route to break economic UN sanction.
North Korea needs to know how far China is willing to go to defend it. China is interested in the status quo: a split Korea that has not fallen to democracy while at the same time not being forced to commit resources to defending it. North Korea is not interested in the status quo, and it seeks to push China to reveal the extent to which they will commit to North Korea. China was willing to commit more resources than the US in 1953 to ensure a split Korea. So we stopped shooting each other on the 38th parallel, and have been looking at each other since. Is the Chinese commitment the same as 1953? This is the real question, because without the same level of Chinese commitment, it doesn't really matter what Kim does to prevent the collapse of the regime, it will be unpreventable.
North Korea is trying to make the world fear it, its leader is trying to establish himself as being not one to mess with despite his youth and inexperience. Nobody thinks they're going to act on any of the war threats they put out there, they're stupid but they're not that stupid.