North Korea puts ‘another piece in puzzle' towards nuclear capability

North Korea's latest missile test has security analysts admitting that the military-led country is closer than ever to possessing a nuclear missile system capable of attacking another country.

On Wednesday, a North Korean submarine-launched missile flew about 500 kilometers east, landing for the first time in Japan's Air Defense Identification Zone (ADIZ).

Pyongyang's official KCNA news agency reported that regime leader Kim Jong Un supervised the test and described it as "the greatest success and victory".

Research Analyst in Proliferation and Nuclear Policy at RUSI, Emil Dall, said to CNBC that Wednesday's launch appears to be North Korea's most successful missile test.

"It demonstrates Pyongyang's continued determination to develop a fully-workable nuclear weapon capability, and this is another piece in that puzzle.

Dall said Thursday it was also probable the rogue state now has a nuclear bomb that can fit on the missile.

"Whether North Korea has been able to construct a nuclear warhead small enough to fit on to an intermediate-range missile is uncertain, but should be assumed at this point," he said via email.

Analysts at the US-Korea Institute at Johns Hopkins University reported on their website on Wednesday that, "While North Korea still faces significant technological challenges, including building of a new class of submarine to carry the missile, it is on track to develop the capability to strike targets in the region, including Japan, by 2020".

Following the test launch, Japanese Prime Minister Shinzo Abe accused Pyongyang of carrying out an "unforgivable act".

A United Nations spokesperson also repeated that the actions were a violation of Security Council resolutions and urged the Democratic People's Republic of Korea to take steps to "de escalate the situation and return to dialogue on denuclearization".

China is widely considered a key player in policing North Korea.

However Emil Dall said actions by the U.S. were causing Beijing to be less cooperative.

"China has, like North Korea, recently been dissatisfied by the deployment of US anti-missile systems to South Korea which it perceives as threatening to its interests.

"The unity towards North Korea on the Security Council is therefore not as strong as it was at the beginning of the year," he said.