REAL life in N,ORTH K,OREA How do Ki.m Jo.ng-un and his people live

The rogue nation". The "greatest immediate threat". North Korea has been called many things, few of them complimentary.

The government has been accused of brutally oppressing citizens while ruthlessly pursuing the development of nuclear weapons.

In the past year it held its fifth nuclear test, launched several missiles and - most believe - assassinated its leader's half-brother using a chemical weapon.

Most recently, it has conducted its first test of what it claims is an inter-continental ballistic missile, a move that - if verified - increases the threat it can pose to its enemies and ratchets up international tensions.

But why is North Korea such a problem - and why can no solution be found? The US and the Soviets divided Korea into two at the end of World War Two. Reunification talks failed and by 1948 there were two separate governments. The 1950-53 Korean War entrenched the split.

North Korea's first leader was Kim Il-sung, a communist who presided over a one-party state, and the grandfather of current leader Kim Jong-un.

It remains one of the world's poorest nations. Its economy is centrally controlled, its citizens have no access to external media and, apart from a privileged few, no freedom to leave.

Most worryingly, it has conducted five nuclear and multiple missile tests that demonstrate progress towards its ultimate goal of building a nuclear missile. There have been several rounds. The most recent, involving China, South Korea, Japan, Russia and the US, initially looked promising.

Pyongyang agreed to give up its nuclear work in return for aid and political concessions. It went as far as blowing up the cooling tower, external at its plutonium production facility at Yongbyon. But then things faltered. The US said North Korea was failing to disclose the full extent of its nuclear work. Pyongyang denied this, but then conducted a nuclear test. So, since 2009, there have been no meaningful discussions.

John Nilsson-Wright, senior fellow for north-east Asia at think-tank Chatham House, says that North Korea, judging from its recent provocations, is not interested in negotiating at the moment.

"This is because Kim is determined to push forward on military modernization, so rationally it is in his interests to delay."