Raccoons are wreaking havoc in this industrial hub sandwiched between the cities of Osaka and Kobe, with people walking their dogs in the evening being attacked seven times since last month.

The raccoons in Japan trace their origins to North America. They are designated as a special foreign species. Although cute, the mostly nocturnal carnivores can occasionally be aggressive.

Amagasaki officials believe the raccoons involved in the attacks are abandoned pets. The city has issued warnings on its website and set traps at several locations.

The officials said the seven attacks took place in a circular area with a 1.5-km radius. Based on witness accounts, the city believes a family of raccoons is attacking people and dogs.

"Raccoons are usually mildly tempered and rarely attack humans," said Mieko Kawamichi, head of the Kyoto-based Kansai Wildlife Research Association. "The raccoons may have faced threats from stray dogs and developed hostility toward dogs."

As Kawauchi noted, the people attacked were all injured while trying to protect their dogs. The city is thus urging people not to walk their dogs in the evening or to carry a stick if they do so to ward off any raccoons.

Abandoned pets have been a public nuisance for years; now they are threatening ecosystems.

The Tama River ecosystem between Tokyo and Kanagawa Prefecture is facing a threat from foreign fish species, many of which were discarded by pet owners.