The man, whose identity has not been disclosed, set fire to a van and himself in front of the Japanese Embassy in central Seoul at around 3:20 a.m. Friday.
According to police and fire authorities, the man stopped his car on the sidewalk outside the entrance of the embassy building, and set fire to the inside of the vehicle.
Flammable substances such as butane gas and gasoline were found inside the van.
Police were looking through security camera footage and questioning building managers and acquaintances of the suspect, to figure out the motive for the crime and details of how he did it.
According to news reports, the man did not leave a suicide note. He is also said to have expressed anti-Japanese sentiments to an acquaintance on the previous day.
The police said that such sentiments were not related to the ongoing trade spat with Japan.
By Kim So-hyun (email@example.com)