Saturday's failed test of a North Korean ballistic missile prompted subway company Tokyo Metro to briefly halt its train lines as a precaution, but criticism has since grown that it overreacted.

On Saturday morning, the private railway shut down all of its train lines for about 10 minutes in response to news that the North had launched a missile. It resumed operations after receiving no further update, spokesman Noboru Ishikawa said.

This was the first time Tokyo Metro had ever taken such a safety precaution, Ishikawa said, adding that the discussions on the emergency measures were held in mid-April.