One person has been killed and at least three injured in twin blasts in Japan.

The explosions occurred at a park in Utsunomiya, about 60 miles (100 kilometres) north of Tokyo, shortly after 11:30 am (0230 GMT), a local fire department spokesman said.

It was not immediately clear what caused the blasts.

"One person was found dead," the fire department spokesman told AFP.

Public broadcaster NHK said a body that had been badly damaged in the blast was found at a bicycle parking space.

One of the injured was being treated for shrapnel wounds, the broadcaster said. The person killed was male, but no other details were available about him or the other two wounded.

Images broadcast by NHK showed two burnt out cars in a car park about 200 metres from the park and a charred broken bench at the edge of the park, where a folk art festival was underway.

Witnesses told the broadcaster they heard a series of loud explosions. A man told NHK that he "smelled gunpowder in the area" after the explosions.