Kim Jong Un strengthens his family's iron grip on power by promoting his sister Kim Yo Jong

Kim Jong Un has overseen a major shakeup of North Korea's government as he promoted dozens of close aides to positions of power.

Among the new promotions is Kim Yo Jong, 30, his sister, who has been elevated to a position within the powerful Central Committee.

The promotion marks a return to favour two years after she was fired as Kim's propaganda chief due to a series of security blunders at rallies around the country, according to Daily Mail.

On one occasion Kim was nearly hit in the face with a guitar by an over-enthusiastic musician as he toured a farm, while on a second occasion he was man-handled by fans at a concert.

Kim Yo Jong's new job will be as an alternative member of the Central Committee - the chief decision-making body over which Kim presides.

"It shows that her portfolio and writ is far more substantive than previously believed and it is a further consolidation of the Kim family's power," said Michael Madden, a North Korea expert at Johns Hopkins University's 38 North website.

Kim made the announcement at the Korean Worker's Party conference in Pyongyang, which is taking place ahead of the anniversary of the party's founding on Tuesday.

The most high-level appointment was the promotion of 67-year-old Choe Ryong Hae, who is known to be one of Kim's closest aides.

Choe, already vice-president of North Korea's ruling party, was handed a position on the Central Military Commission.

He was also thought to have fallen out of favour with Kim after mishandling a power plant project in 2015, but now seems to have regained popularity with Kim.

Kim Jong Sik and Ri Pyong Chol, two of the three men behind North Korea's rocket programme, were also promoted as Kim praised the country's nuclear weapons.

North Korea's nuclear weapons are a "powerful deterrent firmly safeguarding the peace and security in the Korean peninsula and Northeast Asia," Kim said, referring to the "protracted nuclear threats of the U.S. imperialists."

Ri Yong Ho, North Korea's delegate to the UN who branded trump "President Evil" in a speech to the General Assembly, has also been made a full vote-carrying member of central government.

Kim was pictured giving a speech to his politburo in Pyongyang amid rumours that the country is preparing for another missile test.

Anton Morozov, a Russian lawmaker who recently returned to Moscow after a visit to Pyongyang, said the regime informed him of the test while showing him calculations that prove the weapon can range the US West Coast.

He also said the regime assured him that they have a nuclear warhead capable of fitting on a missile and the technology to bring it back down to earth intact.

A likely date for any missile test would be on Monday, ahead of the party founding anniversary and on Columbus Day, a public holiday in the US.

North Korea often times its missile launched to coincide with American public holidays to ensure maximum media coverage.