Firefighters investigate a burnt car at the site of an explosion in Utsunomiya, Japan, in this photo taken by Kyodo October 23, 2016. [Photo/Agencies]

TOKYO - A former Self-Defense Forces (SDF) official evidently committed suicide by blowing himself up with a suspected incendiary device in a popular park in the city of Utsonomiya where a festival was being held on Sunday, local police officials said.

According to the officials, a suicide note saying "I pay with my life" was found among the deceased man's clothing, with local reports also adding the note expressed the suspect, 72-year-old Toshikatsu Kurihara, had been experiencing family problems.

The explosion that killed Kurihara also severely injured three others.

Kurihara's house was also found to have been burned down on Sunday morning at around 11:00 am local time. Investigators said they are currently trying to determine the links between the suicide blast, a second explosion in the vicinity of the park and three cars being burned in a nearby parking lot, one of which belonged to Kurihara.

Multiple explosions were initially reported to have occurred in the vicinity of the popular Utsunomiya Joshi Park during a local festival being held there, with an emergency call being made to the police at 11:40 am local time saying that a series of blasts had been heard and a man was on the ground engulfed in flames.

One person was subsequently found to be lying on the ground in the park without vital signs when rescue officials arrived. His body was described by first responders as being "severely damaged" by the explosions and other reports confirmed that the body had been on fire.

At least one of those seriously injured in the blasts was rushed to a local hospital having been struck by shrapnel from one of the devices, local police also said, with rescue officials adding the person is receiving medical treatment.

Three cars were also reportedly on fire in a coin parking lot close to the park at 11:30 a.m. local time, although no injuries were reported as a result of an explosion there and the burning vehicles.

Witnesses at the scene, as quoted by local media, said the explosions sounded similar to that of a bomb being detonated, with televised reports from Japan's public broadcaster NHK in the area at the time capturing the audio of the explosions, which were both powerful and "thunderous" as described by another witness.

Plumes of black smoke were seen billowing into the sky from the area after the explosion and fires, and those in the vicinity reported smelling what they described as gunpowder, according to NHK.

Utsunomiya lies 100 km north of Tokyo and is an important cultural, political and economic hub in Japan and home to around 440,000 people.

Utsunomiya City Hall is located close to the parking lot, thought to be the site of at least one of the explosions and the park is also situated 500 meters from the Tobu Utsunomiya Station.

Due to its close proximity and ease of access from Tokyo by train, the city and broader region is a popular destination for day trips by Japanese as well as foreign visitors.