Japan has deployed Patriot missiles in its capital as it readies to defend the 30 million people who live in greater Tokyo from any North Korean attack.
Two Patriot Advanced Capability-3 surface-to-air missile launchers had been stationed at the defence ministry in Tokyo before dawn on Tuesday, a ministry spokesman said, while Defence Minister Itsunori Onodera said "we are proceeding with measures including deployment of PAC-3 as we are on alert".
Local reports said PAC-3 will be deployed in another two locations in the greater Tokyo area.
Tokyo's response thus far to the threats emanating from Pyongyang has been low key and Tuesday's moves are the most visible yet that it is rattled.
"The government is making utmost efforts to protect our people's lives and ensure their safety," Prime Minister Shinzo Abe told reporters on Tuesday.