North Korean dictator Kim Jong-un ordered the execution of a singer said to be his ex-girlfriend for violating pornography laws, a South Korean newspaper has claimed.

Pop singer Hyon Song-wol was executed by firing squad along with 11 other entertainers, said Seoul-based Chosun Ilbo, South Korea's largest daily newspaper.

They were arrested for filming themselves having sex and selling the videos. Some of the recordings reportedly surfaced in China.

The executed were members of three of North Korea's most popular music bands, the Unhasu Orchestra, the Wangjaesan Light Music Band and the Moranbong Band.

"They were executed with machine guns while the key members of the Unhasu Orchestra, Wangjaesan Light Band and Moranbong Band as well as the families of the victims looked on," a Chinese source told Chosun Ilbo.

The families of the executed were then interned in a prison camps, the source continued. The Unhasu Orchestra and Wangjaesan Light Music Band were broken up by authorities.

Hyon and Kim Jong-un were said to have known each other since they were teenagers, long before the 30-year-old became supreme leader in 2011.

The couple were reportedly in a relationship 10 years ago but Kim's late father, dictator Kim Jong-il, ordered the relationship to stop.

Hyon reportedly went on to marry a soldier. Kim is married to another singer, Ri Sol-ju who was also a member of the Unhasu Orchestra. The identities of the two women became confused in initial reports.

Hyon Song-wol
Singer Hyon Song-wol, Kim Jong-un ex-grilfriend, was reportedly executed by a firing squad (Courtesy of Chosun Ilbo)