Local authorities in Japan's Yamaguchi city said Monday they are turning to tranquiliser guns to confront marauding monkeys that have injured 42 people in recent weeks.

Japanese macaques are seen commonly across large parts of the country, and are a pest in some areas, eating crops and even entering homes.

But a spate of monkey attacks in the city in western Japan has been unusual, with adults and children suffering wounds including scratches and bites.

"All of Yamaguchi city is surrounded by mountains and it's not rare to see monkeys," a city official from the agricultural department told AFP, declining to give her name.

"But it's rare to see this many attacks in a short period of time."

The injuries have so far been largely mild, but authorities are now turning to tranquiliser guns after traps they set failed to snare any of the pesky primates.

"Initially only children and women were attacked. Recently elderly people and adult men have been targeted too," the official said.

The city isn't even sure if the attacks are the work of multiple monkeys or a single aggressive individual. The intruders have in some cases entered by sliding open screen doors, or entering through windows.

City officials and police have been patrolling the area since the first attacks around July 8, but have yet to snare any monkeys.

The story has made headlines in Japan in recent weeks, with local residents reporting regular invasions.

"I heard crying coming from the ground floor, so I hurried down," one local father told the Mainichi Shimbun daily.

"Then I saw a monkey hunching over my child."