One person has been killed, and at least two injured after a pair of near-simultaneous blasts in a Japanese park on Sunday.

The explosions occurred around noon in Utsunomiya, some 100 kilometres north of Tokyo. Public broadcaster NHK said a body -- badly damaged in the blast -- was found at a bicycle parking space.

Police say one blast hit a car parking lot, the other at a park bench. The smell of gunpowder was reported in the area after the explosions.