A tornado has ripped through the Japanese regions of Ibaraki and Tochigi, killing a 14-year-old boy and causing major devastation.

Roofs were ripped off houses and cars were overturned in the area 60 kilometres north east of Tokyo. There were reports of dozens of injuries, several of them serious.

The twister hit at about 1pm local time, bringing high winds and lashing rain just 20 minutes after the Japanese meteorological agency had issued a tornado warning.

By the time it had passed through, close to 200,000 homes were without electricity.