North Korea has fired what is believed to be a short-range Scud missile off its east coast, according to South Korea's military.
Seoul said the missile flew around 450km after its launch from the town of Wonsan and landed in an area of the Sea of Japan in Japan's maritime economic zone.
Japan's chief cabinet secretary Yoshihide Suga said the launch violated United Nations Security Council resolutions.
"Japan absolutely cannot tolerate North Korea's repeated provocative actions. We have strongly protested to North Korea and condemn its actions in the strongest terms," he said, according to the Associated Press.
There has been no official statement on North Korea's media but earlier, it was reported that the country had tested a new anti-aircraft weapon system which it said it hoped to mass produce and deploy nationwide.
If confirmed, it would be third missile launch by North Korea since the inauguration of the new South Korean leader Moon Jae-In, who has called for a National Security Council meeting to discuss the launch. The White House said that the US president, Donald Trump, had been informed.
Earlier in May, Pyongyang said it had successfully tested an intermediate-range ballistic missile, however western experts say that the country is a few years away from developing a nuclear-armed missile that can reach the US.
Tensions between North Korea and the west have ramped up with the US sending its third aircraft carried-led strike group close to the Korean peninsula.
USS Nimitz, one of the world's largest warships, will join two other supercarriers, USS Carl Vinson and USS Ronald Reagan, which are already sailing in the region.