Kim Jong-un's nuclear general and missile chief have not been seen for weeks

Two of Kim Jong-un's top weapons chiefs have not been seen in public in weeks raising fears North Korea is preparing for another missile test.

Lieutenant General Kim Rak Gyom, who is in charge of the country's nuclear programme, and Ri Man Gon, Kim's chief missile engineer, were both notably absent at two major public celebrations in the last week.

The men are unlikely to have been dismissed, having been praised over the progress of the country's weapon programme, leading to speculation in the South Korean media that they are preparing another test, according to Daily Mail.

North Korea was thought to be preparing a missile launch for October 10, the anniversary of the founding of the Worker's Party of Korea and to coincide with Columbus Day in the US.

While no test materialised on that occasion, it is now thought the hermit state could be preparing another for the 19th Party Congress in China on October 18.

The date is the most important political event to take place in China in years, and will likely be used by leader Xi Jingping to indicate who will take over from him when he stands down at the end of his second term in five years.

While North Korea and China were firm allies, a series of recent sanctions and statements from Beijing urging Kim to end his missile launches have changed that.

Earlier this year the North issued a rare rebuke to China, accusing it of forgetting history and siding with American "imperialists".

Rak Gyom, who is almost always at Kim's side during important public occasions, was missing during a major rally in Pyongyang on Saturday, according to the North Korea Times.

He was also absent for the anniversary of the ruling party's founding on Tuesday. Man Gon was also missing during both events.

Kim inspecting what could be a nuclear warhead. Photo / AP

Sources quoted in the South Korean media said: "There's little chance that Ri and Kim have been dismissed or purged because they've been praised for major achievements recently.

"It's highly likely that they were absent because they'd been given an important assignment."

So far this year the North has already tested the country's first ICBM, which is believed to be able to range most of the United States.

Kim also carried out a nuclear test of what his regime claimed was a powerful hydrogen bomb. Seismic activity from the test seems to confirm the explosion was much larger than previous tests.

The North claims the new bomb is small enough to mount on a missile, though has provided no evidence of this.

It also claims to have technology capable of bringing the warhead to earth intact, though previous ICBM tests seem to contradict this as re-entry vehicles were seen falling to earth in flames.

If the North can surmount these two technical challenges, it will have developed a full nuclear missile capable of ranging American, a step the President Trump has vowed "will never happen".