A city in Japan has closed all its 94 primary and secondary schools after a bear was spotted in the municipality for the first time.

Officials in Utsunomiya, a city of half a million people about 100km (62 miles) north of Tokyo, took action after a medium-sized black bear – estimated to be about one-metre-long – was seen near a park in the city on Saturday. The bear was spotted again on CCTV running just in front of two startled young men in the city centre, in the early hours of Sunday.

It was seen in residential areas during the day on Sunday, and again in a factory district about 2km from the city centre at 4am on Monday.

Utsunomiya City officials are urging residents to keep their doors and windows locked, not to approach the bear if they see it and to take refuge in the closest building. The city has also deployed public address vehicles to alert local residents. Police and the local hunting association resumed their search for the animal this morning.

A record 50,000 bear sightings have been reported this year in Japan, concentrated in the north-east. The animals have not usually been seen this close to Tokyo. However, a Russian hiker was injured by a bear last month in Okutama, on the far western edge of the metropolitan area, while another appeared in the satellite city of Hachioji shortly afterwards.

Last week, a bear in Fukushima who attacked four people entered a company’s office, injuring an employee, before going into a factory, from which it is believed to have escaped by opening a window from inside.

Bear attacks in Japan have been on the increase in recent years, with a record high number of deaths and injuries recorded in the year to March. Local governments are exploring various methods in response, including CCTV cameras linked to AI analysis in an attempt to track their movements.

Precise population numbers are unavailable, but there are estimated to be between 12,000 and 42,000 Asiatic black bears on Japan’s main Honshu island, and numbers are thought to have increased in line with the growth in sightings. They can grow to up to 1.5 metres long and weigh up to 120kg.

The bigger brown bears live only on the northern island of Hokkaido, with males averaging 2 metres in length and can weigh up to 400kg. They are estimated to number about 12,000.

Fluctuations in harvests of bears’ staple foods, including acorns, can bring them into towns and villages to forage. Falling rural populations, particularly of younger people, is thought by experts to make enter residential areas quieter and thus more likely that bears will enter, leading to an increase in encounters with humans.