As many as 50 senior members of the North Korean government and military have been publicly executed so far this year, according to South Korea's intelligence agency.
The victims of the purges - which the National Intelligence Service believes are continuing - include 10 members of the ruling Workers' Party who were executed by firing squad for watching South Korean soap operas, bribery or womanising.
Many of the officials singled out by Kim Jong-un, the North Korean leader, were reportedly close to Jang Song-thaek, Mr Kim's uncle, who was arrested in December 2013 and executed for a series of crimes against the state.
The ongoing elimination of Jang's allies indicates that Mr Kim is getting rid of potential sources of opposition and building his own power base, although executing a member of the party for watching a South Korean television show hints at a trumped-up charge.
Defectors from North Korea have told The Telegraph that pirated versions of South Korean and Chinese television programmes are widely available in North Korea and are frequently traded on the black market.
And despite the North Korean government's efforts to stop its citizens learning about life outside their borders, the proliferation of mobile phones and electronic media that are easy to carry and conceal has made it impossible to keep all foreign influences at bay.
Details on the executions were provided by the intelligence service in a report to the South Korean parliament on Tuesday, Yonhap News reported, while a further 200 officers in the artillery arm of the North Korean military have been demoted due to the poor accuracy of their units in training exercises.
The NIS report also said the North has expanded the capacity of its political prison camps and that hackers in North Korea attempted to access thousands of smartphones in South Korea this year, using programmes disguised within mobile gaming apps.
The report added that while Mr Kim has reappeared in public after undergoing successful surgery to remove cysts from his ankles, his weight many mean that the complaint will return in the future.
By Julian Ryall, Tokyo