At least one person was killed and three others were injured as multiple explosions hit a popular park in Tochigi prefecture in Japan on Sunday, police said.

The explosions in Utsunomiya city were heard in the vicinity of the Utsunomiya Castle ruins park during a popular festival where many people had gathered, Xinhua news agency reported.

The injured were taken to a hospital, an official said.

Cars also reportedly caught fire in a parking lot close to the park following the second explosion a minute later. No injuries have yet been reported as a result of the second blast.

According to the police, the first explosion took place at 11.30 a.m.

A third explosion was also reported almost immediately after the second, although this remains to be confirmed by police officials who have also yet to determine the cause of the explosions.

Witnesses at the scene said the second explosion sounded smaller than the first, with the first being described by one witness as a “tremendous explosion similar to a bomb”.

Others reported plumes of black smoke billowing into the sky from the parking lot after the explosions. While the police confirmed there were two explosions, some witnesses reported hearing as many as four or five loud blasts in quick succession, Japan’s public broadcaster NHK said.

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.

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