One man has been killed and three other people injured when two explosions rocked a park in Utsunomiya, a city in Japan's Tochigi prefecture.
Cars in the parking area were seen burning as police and emergency personnel arrived at the scene.
There was a festival underway in the park when the explosions occurred.
The first blast took place about 11.30am local time and within a minute there was another explosion.
A badly disfigured body was discovered at the parking space.
Japan's state broadcaster NHK quoted an eyewitness who said he heard a loud sound and saw three people lying on the ground. He added that he could smell gunpowder at the blast site.
The cause of the explosions is not known.
A suspected suicide note has reportedly been found at the blast location inside a vehicle, which belonged to a 72-year-old former officer in Japan's Self-Defense Forces – the country's combined military services.
Photos showing charred vehicles from the explosions have been posted on social media.
Utsunomiya is located north of Japan's capital Tokyo.