North Korea fired an unidentified projectile towards the sea off its east coast on Tuesday.
Japan’s defence ministry said it appeared to be a ballistic missile.
The announcement came just before North Korea’s Ambassador to the United Nations Kim Song urged the United States to give up its hostile policy towards Pyongyang.
He said no one can deny his country’s right to self-defence and to test weapons.
Kim Song said the country is just shoring up its self-defence and if the United States drops its hostile policy, it would respond “willingly at any time” to offers to talks.