Kim Jong-un announces changes at line-up of powerful Workers Party's Politburo as he reaffirms N Korea's nuclear drive.
North Korean leader Kim Jong-un has promoted his younger sister to a senior post in the one-party state, according to state media.
Kim Yo-jong became an alternate member of the party's powerful Politburo, the decision-making body presided over by her brother, the official KCNA news agency said on Sunday.
The promotion was announced along with those for dozens of other top officials at a meeting of the Central Committee of the ruling Workers' Party of Korea on Saturday in the capital, Pyongyang.
The Central Committee is one of the leadership committees of the party, consisting of the politburo - the highest executive organ - as well as the secretariat.
Since inheriting power from his father in 2011, Kim has placed his younger sister in various positions in order to strengthen the position of the family within the country's leadership.
She has frequently been seen accompanying her brother on his "field guidance trips" and other events and is known to have been involved in the party's propaganda operations.
Both were born to the late former ruler Kim Jong-il and his third partner, former dancer Ko Yong-hui. The family has ruled North Korea since its creation in 1948.
Writing for Al Jazeera in February, Michael Madden, a visiting scholar at the US-Korea Institute at Johns Hopkins School of Advanced International Studies, described Kim Yo-jong as one of the North Korean leaders "closest aides".
Like her older half-sister, Sul-song, Yo-jong was a favourite child and expressed an early interest in North Korean politics," wrote Madden, who is also predicted that "Yo-jong will be a power player" in North Korean "for a long time to come as her career is just getting started".
Her new position indicates she has become a replacement for Kim Jong-un's aunt, Kim Kyong-hui, who had been a key decision maker when former leader Kim Jong-il was alive.
In January, the US Treasury blacklisted Kim Yo-jong along with other North Korean officials over "severe human rights abuses".
Since coming to power, Kim has overseen four of the country's six nuclear tests - most recently in September - while cementing his grip on power through a series of purges.
Kim Jong-sik and Ri Pyong-chol, two of the three men behind Kim's banned rocket programme, were also promoted.
State media also announced that several other high ranking cadres were promoted to the Central Committee, in what the South Korean unification ministry said could be an attempt by North Korea to navigate a way through its increasing isolation.
"The large-scale personnel reshuffle reflects that Kim Jong-un is taking the current situation seriously, and that he's looking for a breakthrough by promoting a new generation of politicians," the ministry said in a statement.
North Korea's Foreign Minister Ri Yong-ho, who named US leader Donald Trump "President Evil" in a bombastic speech to the UN General Assembly last month, was promoted to full vote-carrying member of the politburo.
"Ri can now be safely identified as one of North Korea's top policy makers," Madden told Reuters news agency.
"Even if he has informal or off the record meetings, Ri's interlocutors can be assured that whatever proposals they proffer will be taken directly to the top," he said.
The announcements came as Pyongyang faces growing global pressure to curb its weapons drive following recent nuclear and missile tests.
Tensions soared as Kim traded verbal threats with Trump, who tweeted on Saturday that "only one thing will work" to tame the isolated nuclear-armed state.
During Saturday's party meeting, Kim acknowledged the country faced with "ordeals" under a "stern" situation, but claimed that its economy had grown this year despite ever-tighter sanctions.
He described the North's atomic weapons as a "treasured sword" to protect it from aggression.
"The nuclear weapons of the DPRK (North Korea) are a precious fruition borne by its people's bloody struggle for defending the destiny and sovereignty of the country from the protracted nuclear threats of the US imperialists," Kim was quoted as saying.