North Korea says it has successfully tested its first "intercontinental ballistic missile" (ICBM). A state television announcement said the missile, which landed in the Sea of Japan yesterday, could hit targets anywhere in the world.
But the US and Russia said the missile had a medium range and presented no threat to either country.
North Korea had increased the frequency of its missile tests, in defiance of a ban by the UN Security Council.
The announcement on North Korea state television said the Hwasong-14 missile test was overseen by leader Kim Jong-un.
It said the projectile had reached an altitude of 2,802km (1,731 miles) and flew 933km for 39 minutes before hitting a target in the sea.
North Korea, it said, was now "a fully-fledged nuclear power that had been possessed of the most powerful inter-continental ballistic rocket capable of hitting any part of the world".
A BBC report said that would enable the country to "put an end to the US nuclear war threat and blackmail" and defended the Korean peninsula, it said.
While Pyongyang appears to have made progress, experts believe North Korea does not have the capability to accurately hit a target with an ICBM, or miniaturise a nuclear warhead that could fit onto such a missile.
Other nuclear powers have also cast doubt on North Korea's assessment, with Russia saying the missile only reached an altitude of 535km and flew about 510km.
David Wright, a physicist with the US-based Union of Concerned Scientists, said if the reports were correct, the missile could "reach a maximum range of roughly 6,700km on a standard trajectory".