SEOUL• Explicit and doctored photos of South Korean girl group Momoland's Nancy (below) have been circulating online, taken by a member of her agency who had secretly filmed her changing backstage.

On Monday, her agency MLD Entertainment issued a statement promising to take legal action against the perpetrator, as well as those who had spread the photos online.

The photos appeared to have been taken while Nancy was undressing backstage at the Asia Artist Awards in Hanoi, Vietnam, in November 2019.

The 20-year-old Korean-American starlet, whose full name is Nancy McDonie, joined Momoland in 2016 as one of the seven winners of reality television show Finding Momoland.

MLD Entertainment said in its statement: "Nancy is suffering from a great amount of mental distress. We hope there will be no more malicious posts related to our artist."

In South Korea, illegally shot video footage and photos of women in intimate scenarios for voyeuristic purposes are known as molka and are a serious problem.

It is not known if the staff member responsible for the photos is still employed by the agency.

However, the agency plans to file civil and criminal charges against the culprit for violating South Korea's Special Act on Sexual Violence and the Information and Communication Network Act.

On Monday, Nancy posted a pensive black-and-white photo of herself on Instagram without a caption, prompting an outpouring of support from her fans.

One Vietnamese fan wrote in the comments: "On behalf of the Vietnamese, I want to send to Nancy and her fans a sincere apology. I'm really sorry and feel so reproachful because of this problem."