Seoul, South Korea - According to the South Korean secret service, North Korea's stricken ruler Kim Jong-un has ceded part of his power to sister Kim Yo Jong and other close confidants.

During a closed-off briefing in the South Korean parliament, the state intelligence service described Kim Yo Jong as "de facto leader number two," the national news agency Yonhap reported on Thursday, citing MPs.

She is responsible for the policy towards South Korea and the US. However, the ruler has not chosen his younger sister or anyone else as his potential successor.

It was suggested that, by delegating authority for state affairs, Kim Jong-un aims to relieve some of the work-related stress and shift "the blame for political failure" away from himself. "Chairman Kim still has absolute authority, but some of it has been gradually handed over."

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It remains unclear how the secret service arrived at its assessment. North Korea is one of the most isolated countries. It is subject to harsh sanctions by the UN Security Council as a result of its nuclear weapons program.

Kim Yo Jong, whose age is believed by South Korea to be 32, has been considered an influential adviser to her brother for several years. In March this year, the party official made the first political statement of her own, in which she reacted with verbal attacks to South Korea's criticism of new North Korean missile tests.

The vice-chairman of North Korea's powerful Commission on State Affairs, Pak Pong Ju, and the new Prime Minister Kim Tok Hun are reportedly now controlling the economic sector. Two other party cadres from the army sector have also been given more powers.