Japanese law enforcement officers have arrested a former senior policeman from Thailand for possessing a loaded gun, officials said Wednesday.

Comronwit Toopgrajank, 60, identified as a onetime Bangkok police chief by the Thai Embassy in Tokyo, was arrested on Monday at Narita airport as he tried to leave the country, a spokesman told AFP.

Officials stationed at the airport discovered a revolver with five live rounds in Toopgrajank's suitcase and arrested him on the spot on suspicion of violating the firearm control law, the spokesman said.

The suspect told police "the gun was his own and was a gift from a friend, and that he had forgotten he had put it inside the suitcase," the official said.

"He entered Japan on June 19, and said he visited a waste incineration plant as part of a group of some 80 people," the police official added.

The suspect was later sent to prosecutors, where he was being quizzed, a Thai embassy official told AFP.

While Japanese police do carry guns, Japan has very strict firearms control laws and few people possess weapons or have ever come into contact with them.