President Yoon Suk-yeol, right, alongside his wife Kim Keon-hee, bows during his inauguration ceremony in front of the National Assembly in Seoul, May 10. Yonhap

A police officer investigating the corruption case allegedly involving first lady Kim Keon-hee and her mother was one of the special guests invited to President Yoon Suk-yeol's inauguration ceremony, an official said Thursday.

The lieutenant, whose identity has been withheld, was invited to the ceremony held at the National Assembly complex in May for his role in preventing core technology from leaking overseas, the official at the interior ministry said.

The officer was among 700 special guests, such as firefighters, soldiers and public officials.

Earlier, similar controversies arose that the son of a businessperson under investigation over a stock manipulation case allegedly involving Kim attended the ceremony.

Despite the opposition party's demand, the presidential office has said it is difficult to confirm the list of attendees at the inauguration ceremony. (Yonhap)