Japanese officials say they have found human flesh and hair inside the stomach of a black bear they shot dead after a series of deadly attacks. Authorities in the mountainous Akita prefecture in the north of the country, had warned residents to stay away from forests after police found the badly mauled corpse of a 74-year-old woman on Friday 10 June.

The discovery of the woman, named as Tsuwa Suzuki, appears to be the latest in a series of fatal bear attacks in the region. In May, three men, two in their 70s and one in his 60s, were killed in separate incidents while they were out harvesting bamboo shoots.

After the attacks, local police and firefighters mounted daily patrols in the mountains asking any civilians to leave the area. Then, later on Friday, just a short distance from where the woman's body was found, a female black bear was shot dead.

Regional official, Hideki Abe, told the AFP a "piece of human flesh" was found inside the dead bear's stomach after it was examined but said it was not confirmed that this was the killer bear. It is thought that the bear may not have been alone in carrying out the attacks.

He added that "two thirds of the stomach was filled with bamboo shoots" meaning that the bear had consumed only a little human flesh.

When Japanese authorities found Suzuki they were unable to identify her body due to the severity of her injuries. According to reports from Japan she had gone to forage for edible wild plants.

A local vet said afterwards that the victims may have been all killed by the same bear. "After tasting human flesh (for the first time), the bear may have realised that it can eat them," said Takeshi Komatsu to the Kyodo news agency.

Fatal bear attacks in Japan are rare but the latest casualties mark a sharp spike in the average number of people killed. Before the four recent deaths, only eight fatalities were recorded between 1979 and 2015.

Sightings of bears have also increased in northern Japan with more than 1,200 brown bears and black Asiatic bear sightings registered – nearly double the figure from last year.

Further north, in Hokkaido, seven-year-old Yamato Tanooka had to be rescued after his parents abandoned him by the side of a road as punishment for throwing rocks during a family outing. He was left near a bear-infested forest but despite spending nearly a week in the forest he was found unharmed in a disused military building.