Bear attacks have shot up in Japan this year and sightings of the animals have spiked, a trend blamed on climatic changes and shifting land use patterns, officials and media reports said Wednesday.

At least four people were killed and 80 wounded in bear attacks between April and September in the island-nation, much of which is covered in mountain forests, topping last year's total of 64 attacks, said broadcaster NHK.

Some 400 bears were shot dead near human-populated areas by authorised hunters on Japan's far-northern island of Hokkaido alone, where two people were mauled to death by bears earlier this year, a local official said.

In the mountainous central prefecture of Fukushima, northeast of Tokyo, more than 150 bears were shot dead after they encroached on residential areas.

Some wildlife experts have blamed a record heat wave this summer which impacted the omnivores' natural food sources and sent the Asiatic black bears foraging for food in more densely populated farming and residential areas.

"The extremely hot summer and other climatic factors may have led to a shortage of acorns or nuts in woodlands this year," said Tatsuo Sato, an official of the Fukushima prefectural government.

In some areas habitat destruction is blamed for forcing the bears into closer contact with humans. In other parts, farms are being abandoned and reclaimed by nature, reducing buffer zone with the bears' natural habitats.

In the latest reported encounter, police and hunters went on the hunt Wednesday in Fukuchiyama, Kyoto prefecture, after a one-metre (three-foot) tall bear was sighted in a residential area. Noone was injured.

Another bear was hit by a train on Tuesday in Shiga prefecture, central Japan, a railway company official said.

"We should be fully aware that bears are expanding their range into our living areas," said an official in Hokkaido, which is home to 1,800-3,600 bears.

He also offered some safety advice to local residents: "In the unfortunate case of a bear encounter, all we should do is look steadily into its eyes and move away slowly without running".