"An election that's important to our country is taking place, and we must work together and follow through on it."
He was also due to appear at a stop later Saturday afternoon in Chiba, east of Tokyo.
"That something like this happened in the middle of an election campaign that constitutes the foundation of democracy is regrettable. It's an unforgivable atrocity," Hiroshi Moriyama, the ruling Liberal Democratic Party's election strategy chairman, told NHK.
Security at local campaign events in Japan can be relatively relaxed, in a country with little violent crime and strict gun laws.
