Kim Jong Un's mysterious sister was promoted, cementing her place in North Korea's leadership

• Kim Yo Jong got a big promotion within North Korea's leadership, state media reported.
• She was named to the State Affairs Commission, the country's top decision-making body.
• The role is the biggest one yet for Kim, who was already North Korea's most powerful woman.

The sister of North Korean leader Kim Jong Un has been promoted to become a member of the country's top decision-making body, state media reported on Thursday.

State media reported that Kim Yo Jong was named to the State Affairs Commission, which is the top policy-making group in the country, Agence France-Presse reported.

She already has a leading role in North Korea's government, and is the most powerful woman in the country. But this new role is her biggest yet, CNN noted.

The promotion also likely increases speculation that she could be named as her brother's successor, AFP reported, though the report noted that she was still "long-shot candidate."