North Korean leader Kim Jong-un visits the revolutionary battle site at Mt Madu in South Pyongan province in an undated photo released in January. (Photo/CFP)

North Korean supreme leader Kim Jong-un has put to death multiple family members of his former mentor and uncle-in-law Jang Sung-taek, whom Kim executed last month for treason, reports the Seoul-based Yonhap News Agency.

According to Yonhap's "multiple sources," Kim is attempting to completely destroy all traces of Jang's existence through "extensive executions" of his family, including the children and grandchildren of all close relatives. Jang, who was put to death on Dec. 12 last year, was described as "despicable human scum" by state media and accused of treason, corruption, womanizing, gambling and taking drugs. He was married to Kim's aunt Kim Kyong-hui, who is believed to have survived the fallout but is rumored to have either committed suicide or passed away from illness since her husband's death.

Those reportedly killed in Kim's purge include Jang's sister Jang Kye-sun, her husband and ambassador to Cuba, Jon Yong-jin, and Jang's nephew and ambassador to Malaysia, Jang Yong-chol. The nephew's two sons were also said to have been killed.

All the relatives were allegedly called to Pyongyang around the time of Jang's execution. All the sons, daughters and grandchildren of Jang's two older brothers are also believed to be among those killed.

"Some relatives were shot to death by pistol in front of other people if they resisted while being dragged out of their apartment homes," Yonhap quoted a source as saying.

Some members of the family related to Jang via marriage are said to have been spared and sent to remote villages with their maiden families, Yonhap said, though low-level officials linked to Jang have been unable to escape the purge.

The reports have not been independently verified, though Yonhap, which has close links to the South Korean government, is regarded as one of the more reliable sources of North Korean news.