South Korean news agency Yonhap claims the entire family of purged military leader Jang Song-thaek has now been executed, and several children were killed in the purge.
Jang, North Korean leader Kim Jong-un's uncle, was executed in December after he was accused of attempting to overthrow the regime.
"Extensive executions have been carried out for relatives of Jang Song-thaek," one source said on condition of anonymity.
"All relatives of Jang have been put to death, including even children."
The report suggests that Jang's two brothers were executed, along with their sons, daughters and grandchildren.
The purge also allegedly claimed the life of Jang's sister Jang Kye-sun as well as her husband, Cuba ambassador Jon Yong-jin, and Malaysia ambassador Jang Yong-chol, who was a nephew of the general.
"Some relatives were shot to death by pistol in front of other people if they resisted while being dragged out of their apartment homes," a source said.
"The executions of Jang's relatives mean that no traces of him should be left," another revealed.
"The purge of the Jang Song-thaek's people is under way on an extensive scale from relatives and low-level officials."
Some relatives by marriage have reportedly been spared their lives and they are believed to have been sent to remote villages.
Yonhap's report, which is yet to be corroborated, is based on a single anonymous source, leading many to question its authenticity.
Some experts have even suggested China has used the Beijing-controlled newspaper Wen Wei Po to spread anti-North Korea propaganda.
The publicly-funded Yonhap agency, which has close links to the South Korean government and intelligence services, has been wrong in its reports on the North in the past, according to independent website nknews.org.
Sceptics can also point to a recent hoax which claimed the uncle of North Korea's leader Kim Jong-un was executed by being devoured by 120 starving dogs.
However, the latest report is given credence by North Korea's history of "guilt by association", an approach which has seen entire families subjected to heavy punishment simply for being related to political dissidents and defectors.
Before his execution, Jang was often pictured beside Kim. He was married to the dictator's aunt and was known as his nephew's mentor following his accession to power in 2011.
Jang, 67, was killed just days ahead of the second anniversary of Kim's father Kim Jong-un's death.