North Korea says it has successfully tested a new type of intercontinental ballistic missile (ICBM) that can reach the whole of continental United States.
State television said Pyongyang had achieved its mission of becoming a nuclear state.
The Hwasong-15 missile, described as its "most powerful", was launched in darkness early on Wednesday.
It landed in Japanese waters but flew higher than any other missile the North had previously tested.
The test, which defied international sanctions imposed over the North's weapons programme, drew swift international condemnation, with the UN Security Council due to convene an emergency session.
South Korea responded by carrying out live-fire drills, launching one of its own ballistic missiles.
News of the launch was announced on state television in a special broadcast at midday, as well as in a report released by state news agency KCNA.
Pyongyang says the missile reached an altitude of 4,475km (2,780 miles) and flew 950km in 53 minutes, close to independent estimates made by South Korea's military.
The projectile, fired at a steep incline, did not fly over Japan as some have done in the past, and landed about 250km short of its northern coast, according to Japanese officials.
North Korea has previously said that its projectiles can hit the US but this marks the first time it says it can do it with this new type of missile, which appears to be an upgraded version of previous models.
KCNA added that North Korean leader Kim Jong-un, who personally signed off on the launch, "declared with pride that now we have finally realised the great historic cause of completing the state nuclear force, the cause of building a rocket power"
The report said that "as a responsible nuclear power and a peace-loving state", North Korea would "make every possible effort to serve the noble purpose of defending peace and stability of the world".
It said its weapons, meant as a defence against "the US imperialists' nuclear blackmail policy", would "not pose any threat to any country" as long as North Korean interests were not infringed upon.
"This is our solemn declaration."