A Japanese man puzzled by food mysteriously disappearing from his refrigerator got a shock when he found out a woman had been living in his home for months without permission, police have said.

The 57-year-old man living alone - or so he thought - in the western city of Fukuoka installed a security camera and called the police when he saw images of someone walking around his home while he was out.

"We searched the house in the man's presence. We found the woman in the closet," said a local police spokesman.

The woman, named as 58-year-old Tatsuko Horikawa, was found in a flat storage space only just big enough for a person to squeeze into lying down.

She had sneaked a mattress and several plastic bottles into the cubby hole, police said, adding that the woman had been arrested.

"She told police that she had nowhere to live," the spokesman said.

"She seems to have lived there for about a year, but not all the time."

It is unclear how she managed to enter the home undetected. Police suspect she might have been closet-hopping, moving from house to house.

- AFP