Japan on Thursday marked the 81st anniversary of the dropping of atom bombs on its cities of Hiroshima and Nagasaki by US. "Downplaying the inhumanity of nuclear weapons...could ultimately result in another Hiroshima or Nagasaki," said Hiroshima's Mayor Kazumi Matsui. "I pledge to devote every effort to achieving a world without nuclear weapons and lasting peace," PM Sanae Takaichi said.