Some analysts suggest North Korea used the protest as a pretext to reject calls for a dialogue with the South.
Fighter jets from the US and two key allies roar during annual exercises that have gained importance as the Asia-Pacific region responds to China’s rise.
Japan says it may fire warning shots to keep foreign aircraft out of its airspace, raising concerns that its territorial dispute with China could escalate.
Hiroshima marks the 67th anniversary of the world’s first atomic bomb attack with a call for the elimination of nuclear arsenals.
Japan reportedly has evidence that a Chinese company exported vehicles to North Korea capable of transporting and launching missiles in possible violation of UN sanctions.