Monday's inflammatory remarks by Chief Cabinet Secretary Shinzo Abe in the wake of North Korea's missile tests have touched off a controversy over Japan's interpretation of "pre-emptive attacks."
South Korea criticized Japan for floating the idea, saying it revealed Japan's "expansionist nature" as a former colonial power.
"We can't help but intensely watch it, as Japan exposed the nature of its aggressive policy," Yonghap News Agency quoted spokesman Jung Tae Ho as saying at the South Korean president's office.