Corruption has been revealed in the Japanese sport of kendo, as the All Japan Kendo Federation said Friday that people taking promotional exams had often been paying money to their examiners in order to win their approval.

The federation said it had found a case of a person paying a sum of 1 million yen to seven examiners of iaido, a type of martial art based on the drawing of a sword, and another case in which someone paid 2 million yen to examiners through an instructor in 2016. Neither of them passed the exams.

The revelation comes after a man recently filed a complaint with a committee of the Cabinet Office, alleging he was asked by multiple examiners to pay a total of 6.5 million yen in cash when he was taking an exam in 2012, according to a source close to the matter. The federation said it was unable to obtain evidence supporting the man's claim through its own probe.

Yukimichi Nakatani, executive director of the federation, said he considers the corruption a "serious issue."

"This is something that should not have happened," said Nakatani, adding the federation has already taken preventive steps including keeping the names of examiners undisclosed until the day of the exams.

The federation also imposed penalties on those involved in the cases, including suspensions of their membership and rank, but not on those who admitted to the allegations and had shown remorse, it said.