JOHANNESBURG (Reuters) - South African prison authorities apologized on Monday after pictures circulated on social media showed inmates being entertained by women dressed in knee-high boots and lacy lingerie while wardens looked on.

In one image two women can be seen pulling at the trousers of a shirtless inmate, while another shows a scantily-clad woman embracing a grinning man in orange prison-issue clothes.

Wardens in full uniform and more than a dozen inmates can be seen watching on in a prison yard.

The saucy show took place on June 21 at the Johannesburg Medium Security Prison during celebrations for Youth Day, an annual public holiday on June 16 that marks the 1976 killing by police of students protesting against racially-segregated education.

“The intention was never to have strippers or dancers in the facility. The dancers were obviously not approved,” said James Smalberger, acting National Commissioner of the Department of Correctional Services.

“We want to apologize to the citizens of South Africa for this incident which, indeed, is very disturbing.”

Smalberger said 13 officials had been suspended pending a full investigation.