The Japanese government says it's closely monitoring North Korea for further provocative actions following the announcement it had carried out a test "of great significance" at a rocket launch site.
North Korea's Academy of National Defense Science released the statement on Sunday.
The Japanese government suspects the test at the Sohae Satellite Launching Ground involved ballistic missiles.
The North has previously used the site to fire what were believed to be long-range ballistic missiles and conduct missile engine tests.
A senior Japanese Defense Ministry official says North Korea may have carried out a test to extend the range of long-range ballistic missiles.
The official indicated that Pyongyang might be trying to rattle Washington.
North Korea has set a yearend deadline for the US to come up with a breakthrough in denuclearization talks. It has also raised the possibility of taking countermeasures.
The Japanese government is concerned the North may take further provocative actions, such as firing off more missiles.