Tokyo police have sent papers to prosecutors on a former counselor at the Embassy of Singapore in Japan who is alleged to have secretly filmed a naked teenager at a public bath in the capital.

The Tokyo Metropolitan Police Department referred Sim Siong Chye to prosecutors on Thursday on suspicion of violating laws banning child pornography and others.

Police say the 55-year-old allegedly took the video of a boy and others with a smartphone in a bathhouse changing room in February. The man was working at the embassy at the time.

Police rushed to the scene after receiving a call from a bathhouse employee. During questioning, the man reportedly admitted to filming the video, but refused to voluntarily accompany officers to a police station or submit his smartphone, citing his diplomatic immunity from arrest.

He returned to Singapore in April.

Tokyo police asked the man to turn himself in through Japan's Foreign Ministry in May. He reportedly agreed to the request and came to Japan this month.

Diplomats are exempt from being prosecuted in their host country. Police say the man no longer has diplomatic immunity.

The former counselor reportedly told investigators during voluntary questioning that he had taken videos several times. The man said he came to Japan to express his regret and speak as an ordinary citizen.

The man also reportedly explained that he filmed the video to watch it later by himself, and that he had no intention of targeting children.

Police say it is unusual for diplomats to return to their host countries to respond to police questioning over alleged misconduct.