Kim Jong-un’s uncle, Jang Sung-taek, lost his position as vice-chairman of North Korea’s top military body, South Korean media reports say.
Citing South Korea’s intelligence agency, they say Jang Sung-taek, 67, has been removed from his post.
Two close aides were also executed for corruption, according to the reports.
If confirmed, Jang Sung-taek’s removal would be the biggest upheaval in North Korea’s leadership since Kim Jong-un succeeded his father, analysts say.
Kim Jong-un took over after his father Kim Jong-il died in 2011.
The latest reports emerged from an intelligence briefing given to South Korean lawmakers.
The National Intelligence Service (NIS) made the assessment based on information provided by multiple sources, the South’s Yonhap news agency said.
It also quoted the intelligence service as saying two of Jang Sung-taek’s closest associates had been executed in public in late November.
However, the reports are difficult to verify, and South Korea’s spy agency has been proven wrong before. But if true, the development would mark a significant shift.
Jang Sung-taek, who is married to Kim Jong-il’s sister, was seen by some observers as the power behind the throne.
He climbed through the ranks of the secretive leadership of North Korea’s Korean Workers Party (KWP) in the 1970s. In 1992, he was elected to its Central Committee.
However, Jang Sung-taek has been targeted by purges in the past. In 2004, despite his place in the Kim family, he disappeared from public view.
One report at the time, citing South Korean intelligence, said Jang Sung-taek had been placed under house arrest. Others suggested he had been sent for “re-education”.
However, two years later Jang Sung-taek appears to have been reinstated. He was regarded as an economic reformer and a major influence on Kim Jong-un.
Jang Sung-taek held key positions in both the Communist Party and the National Defense Commission.