Police are searching for a group of men who broke into a house in rural Minamiaizu, Fukushima Prefecture, restraining a woman in her 60s and robbing her early Tuesday, amid a spate of similar robberies in nearby prefectures.

While police are investigating the case as a robbery and assault, they are also examining any possible connections to several similar cases in the nearby prefectures of Tochigi, Nagano, and Gunma that started late last month, in which houses in sparsely populated mountainous areas were targeted.

In Tuesday's case, the assailants entered the house at around 1:05 a.m. while the woman, who lives alone, was sleeping. They tied her up with adhesive tape and demanded money, taking more than ¥10,000 ($64) from her purse.