Tokyo, Japan - A bear attack left four people injured in two factories and a residential area in northern Japan's Fukushima on Tuesday, police and media reports said.

A record 13 people were killed by bears in Japan last year, and there has been a jump in sightings as the animals emerge hungry from hibernation.

"A bear-related human injury incident... occurred in Fukushima City, injuring four people," the prefectural police said in a statement.

The bear was first spotted in a car parts factory, prompting an emergency call explaining that "employees had been bitten," the Yomiuri Shimbun daily reported, citing police and fire department officials.

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As the bear continued its rampage, two other people were injured, one in a residential area and the other on the premises of an electronic equipment manufacturer nearby, the Yomiuri said, adding that the animal was thought to have remained inside the factory.

The report said one of those attacked was severely injured, while the rest only suffered mild injuries.

In the last fiscal year to March, bear sightings nationwide topped 50,000, more than double the previous record set two years earlier, according to official data.

The animals were seen entering homes, roaming near schools, and rampaging through supermarkets and hot spring resorts on an almost daily basis.

Record sightings have been reported again this year as the bears emerge from their winter slumber, according to local media.

In April, bear attacks killed one person and injured five others, according to the environment ministry.

There have also been more than a dozen bear sightings reported on the outskirts of Tokyo this year. Last month, a Russian man in his 30s was mauled while hiking.