Police have dropped a defamation probe into a senior Japanese diplomat accused of making disparaging remarks against President Moon Jae-in's efforts to improve relations with Tokyo, considering his diplomatic immunity, officials said Friday.

Hirohisa Soma, former deputy chief of mission at the Japanese Embassy in Seoul, came under fire after he told a South Korean reporter during a lunch meeting in July that Moon's efforts to improve ties with Tokyo were tantamount to "masturbation."

Japanese Ambassador Koichi Aiboshi expressed regret, and Soma was recalled home.

Police opened an investigation into his remarks after a civic group reported him on charges of defaming and insulting the president but have ultimately decided not to further proceed with the case in consideration of diplomatic immunity, officials said.

"An investigation and court procedures can be pursued only after diplomatic immunity is given up expressly," a police officer said, adding that the foreign ministry has concluded that he practically refused to do so, having returned to Japan. (Yonhap)