AUSTRALIA'S venomous redback spider, first sighted in Japan 17 years ago, is crawling towards Tokyo, with at least one of the creepy-crawlies found in a neighbouring city, officials say.

A man in Kawasaki, which borders southern Tokyo, used an insecticide to kill a strange spider and three egg sacs found inside a sprinkler in his garden on Monday, authorities said.

City officials later confirmed the insect to be a redback, which the national government has labelled an invasive alien species deemed a menace to the country's ecosystem.

The Environment Ministry said redbacks had been found in 23 of Japan's 47 administrative districts. The district including Kawasaki is the closest the spiders have been detected to Tokyo.

"They are presumed to have spread their habitats widely in Japan as they were carried while nestling in cargo, containers, construction materials, automobiles and such" after possibly arriving by sea originally, the ministry said on its website.

"I myself feel that they have come so close," Katsutoshi Oikawa, an environmental official at Tokyo's metropolitan government, told AFP on Wednesday.

"We have not yet proactively worked out measures. But we have been responding to individual inquiries from citizens about ways to deal with the spiders."

Redback bites, which inject a potent neurotoxin, have caused numerous deaths in Australia, although an antivenom stocked in hospitals has prevented fatalities more recently.

Redbacks were first spotted in Japan in 1995 around Osaka, a major port where, experts believe, they may have arrived in a container of Australian woodchips used to make paper in Japan.