The report was published by one of South Korea's most read newspapers, The Chosun Ilbo, which cited unnamed "sources in China."
It said that singer Hyon Song-wol was arrested on Aug. 17 for breaching the country's laws on pornography. Hyon was reportedly executed in public, by a firing squad using machine guns, on Aug. 20 along with around 11 other members of the state-run Unhasu Orchestra and the Wangjaesan Light Music Band.
The victims "were accused of videotaping themselves having sex and selling the videos," according to the report, and some "allegedly had Bibles in their possession, and all were treated as political dissidents."
But to what extent the salacious and gruesome details are to be believed remains an open question.
While there were numerous public reports Tuesday about the high-profile arrival of former NBA player Dennis Rodman in Pyongyang, accurate information about executions, like much else of what transpires in North Korea, is difficult to come by. And details about the personal lives of the country's rulers are guarded particularly closely.
The Hermit Kingdom, as North Korea is sometimes known, ranked second-last on Reporters Without Borders' most recent press freedom survey, two spots behind Syria. Television, radio, telephone networks and the internet are controlled by the government in such a way as to minimize contact between the East Asian country's 24 million people and the rest of the world.
Those tight controls also mean information about current events in the country is sometimes relayed by word of mouth, often by Chinese officials, North Korean refugees who have fled the authoritarian regime or businessmen who travel to the country for work, said Rodger Baker, vice-president of East Asia analysis at global intelligence company Stratfor.
The accounts can become exaggerated as they're relayed from one person to another, he said.
"I'm not justifying the regime or saying that regime doesn't do very horrible things. But North Korea is one of those places that's very difficult to verify information that's coming out," he said.
Even U.S. spy agencies, armed with multibillion-dollar budgets, admit they have been unable to learn about key aspects of the North Korean state.
According to a report last week in the Washington Post, which obtained a secret U.S. budget document from ex-CIA contractor Edward Snowden, the government of North Korea may be considered “the most opaque.”
"There are five 'critical' gaps in U.S. intelligence about Pyongyang's nuclear and missile programs, and analysts know virtually nothing about the intentions of North Korean leader Kim Jong-un," the paper said.
Kim Jong-un's regime "still thrives on a sense of secrecy and a sense of uncertainty," Baker said. "I don't doubt that [North Korean officials] themselves spread some of these rumours. It's a benefit to them. It keeps people overseas thinking, 'These guys are really crazy, maybe we ought to be careful how we deal with them.' "
If the executions did happen, Baker believes the victims' crime could have involved "making connections overseas" or bringing material into the country that was banned by Pyongyang.
Culture of mythmaking
Muddying the waters further, government officials will embellish details of executions as a way to instill fear in the North Korean public, said Randall Baran-Chong, executive director with HanVoice, a Toronto-based advocacy group for North Koreans.
He pointed to unverified reports last year about the execution of Kim Chol, the vice-minister of the army, who was supposedly killed by a mortar shell so that no trace of him would be left behind.
"They like to spread rumours to act as a deterrent," Baran-Chong said. "North Korea is based on these myths and legends … They're a great storytelling culture."
However, there have been signs that Pyongyang's monopoly on information may be starting to loosen — if only slightly. The Associated Press was able to open a news bureau in the capital in 2012. And residents near the border in the north are now able to access Chinese cellphone signals, Baran-Chong said, presumably with phones that have been smuggled into the country.
Seong-min Lee, a 26-year-old North Korean defector, said before fleeing he was able to get his hands on South Korean dramas and documentaries about other countries by crossing the frozen Yalu River into China and back.
"That was really helpful, to know about the outside world," Lee said by phone from Toronto, where he's completing a training program put on by HanVoice.
Lee crossed the Yalu River for the last time in late 2009, making his way across China to Laos, before settling in South Korea.
He said he loves the freedom he enjoys living abroad, particularly the freedom to travel as he likes.
But he is skeptical about the report on the execution of Kim Jong-un's ex-mistress. When it comes to the private lives of the country's autocratic rulers, he said, "everything is top secret."