An unidentified man was detained Tuesday afternoon after starting a small fire in an office building for House of Councilors lawmakers near the Diet building, police said.
The man apparently soaked some newspaper in oil and set fire to it, they said.
The blaze began at around 5 p.m. in a corridor on the third basement level but was soon extinguished, according to the Upper House secretariat. The building is across the street from the Diet building.