North Korea has confirmed that it "successfully" fired a ballistic missile on Sunday in a test supervised by leader Kim Jong-un.
The device was described as a "surface-to-surface medium-to-long-range ballistic missile", the Korean state news agency KCNA reported.
South Korea's defence ministry called it an armed provocation to test the response of US President Donald Trump.
North Korea's latest ballistic missile test has been widely condemned.
KCNA reported that the test of the Pukguksong-2 missile, a new type of strategic weapon said to be capable of carrying a nuclear warhead, was supervised by leader Kim Jong-un.
It added that the missile was fired at a high angle in consideration of neighbouring countries.
South Korea and US officials said the missile flew east towards the Sea of Japan for about 500km (300 miles).
South Korea's defence ministry called it an armed provocation to test the response of US President Donald Trump.
Japan's Prime Minister Shinzo Abe, standing next to Mr Trump on a visit to the United States, said the test was "absolutely intolerable".
United Nations resolutions forbid North Korea from carrying out ballistic missile tests - part of wider efforts to prevent it becoming a fully nuclear-armed power.
South Korea's foreign ministry said that "North Korea's repeated provocations show the Kim Jong-un regime's nature of irrationality, maniacally obsessed in its nuclear and missile development".
'Hostility'
Nato also condemned the missile test, with Secretary General Jens Stoltenberg urging North Korea "not to raise tensions further and to re-engage in a credible and meaningful dialogue with the international community".
The European Union joined the criticism, declaring in a statement that North Korea's "repeated disregard of its international obligations is provocative and unacceptable".
As for the US, Mr Trump said on Saturday: "America stands behind Japan, its great ally, 100%."
Top Trump adviser Stephen Miller told Fox News Sunday: "The message is that we are going to reinforce and strengthen our vital alliances in the Pacific region as part of our strategy to deter and prevent the increasing hostility that we've seen in recent years from the North Korean regime."