Rogue state North Korea is reportedly preparing to conduct a fifth nuclear test and is also believed to be planning to launch a ballistic missile with a range of 3,000 km (1,800 miles). The developments come as US President Barack Obama warns Kim Jong-un that the US could destroy North Korea with its own arsenals, but conceded the humanitarian costs would be great.

North Korea is said to be preparing a mid-range Musudan missile, which could reach Japan and the US territory of Guam. It is thought that an earlier version of the Musudan was fired unsuccessfully earlier in April. Earlier in April, the secretive state also launched a missile from a submarine.

South Korea's Yonhap News Agency said the unsuccessful launch took place on 15 April, which is the birthday of King Jong-Un's grandfather, North Korea's founder Kim Il Sung who despite dying in 1994, is still the country's head of state.

It is thought a fifth nuclear test may also take place to coincide with the Workers' Party Congress in early May.

North Korea usually increases its activity to coincide with the annual US-South Korean military drills which end this week. The North believes the drills are preparation for an invasion and in a statement the DPRK's official news agency KCNA said: "The US's continued pursuance of an extreme hostile policy and nuclear threat and blackmail against the DPRK will only make the latter make drastic progress in bolstering nuclear attack capabilities."

Barack Obama says he is concerned about the North Korean regime which has repeatedly threatened to attack the US and its allies. "We could, obviously, destroy North Korea with our arsenals," Obama told CBS. "But aside from the humanitarian costs of that, they are right next door to our vital ally, [South] Korea."

The US is considering the deployment of the latest anti-missile defence, called a Terminal High Altitude Area Defence System (THAAD), to protect its allies South Korea. However such a system would also potentially reduce the threat from China's own nuclear missiles, so China would be strongly opposed to the deployment of THAAD in the region.