In them, a distressed young woman - who does not appear to be Chinese - is forcibly led into a room and strapped to a gurney, and a Caucasian man wearing a white coat and surgical mask appears to administer an injection .

Later images show the woman in mental and physical anguish before she seems to die. The final image shows her lying motionless with the front of her dress open almost to the point of exposing her breasts.

The series is entitled: "An actual record of the execution of a female inmate: Unveiling the world's darkest side."

The images carry the logo of a local military affairs website. That website, however, said it came from a private post on a mainland internet site.

The China-based website Shanghaiist said the images came from a pornographic website, where one of them was visible, titled "Lethal Injection".

The photo gallery is not the first time Chinese media have been caught out, apparently by inadequate fact-checking.

In November, the website of reported that North Korean strongman Kim Jong-un had been named the "sexiest man alive", treating a spoof award by satirical US website The Onion as genuine. It later deleted the report.

In a 2011 report on an Air Force training exercise, state broadcaster China Central Television used footage from the 1980s Hollywood film

The mainland does not announce statistics about how many people it executes but rights groups say it puts more people to death than the rest of the world combined.

Executions were once carried out by a single shot to the head from close range, but are now mostly by lethal injection.