Multiple blasts in a park area of the Japanese city of Utsunomiya have killed at least one person and injured at least two, emergency services say.

The explosions took place almost simultaneously at about 11:30 local time (02:30 GMT) in the city in Tochigi prefecture, north of Tokyo.

Tokyo-based broadcaster NHK World broadcast images showing two burnt-out cars in a parking area.

It was not immediately clear what had caused the explosions.

Kyodo news agency said a festival celebrating traditional culture had been taking place in a nearby park, where at least one of the explosions was reported to have taken place.

A man who was in the park at the time told NHK that he heard "a big sound" and smelled gunpowder.

The broadcaster also reported that a video camera at nearby Utsunomiya station recorded the sound of three explosions in quick succession - at 11:31, 11:32, and a third "bigger sound" 15 seconds later.

Photos posted to social media appeared to show a column of black smoke rising from the area.

Police have cordoned off the area.