South Korea’s military said North Korea has conducted another missile test.
The White House said the medium-range missile had a shorter range than those used in North Korea’s last three tests.
It comes a week after North Korea tested what it said was a new type of rocket capable of carrying a large nuclear warhead.
Last Monday, the UN Security Council again demanded that Pyongyang conduct no further such tests.
It stressed the importance of North Korea “immediately showing sincere commitment to denuclearisation through concrete action”.
South Korea’s foreign ministry said the launch was “reckless and irresponsible”.
The latest missile flew about 560km (350 miles) towards the Sea of Japan, South Korea’s Joint Chiefs of Staff said. Last week’s missile travelled about 700km.
Japanese news agencies said the missile probably fell into the sea outside Japanese waters.
Japan’s Chief Cabinet Secretary Yoshihide Suga told a news conference a protest had been lodged with North Korea.
North Korea is known to be developing both nuclear weapons – it has conducted five nuclear tests – and the missiles capable of delivering those weapons to their target. Both are in defiance of UN sanctions.
South Korea said the latest test was conducted in Pukchang, in the west of the country. A missile exploded soon after take-off from Pukchang last month.
Earlier on Sunday, the North’s state-run media had said it would continue to launch more “weapons capable of striking” the US.
In early May, the US said a missile defence system it had installed in South Korea was now operational.
The Thaad system can intercept North Korean missiles, although full operational capability is still some months away. North Korea and its ally China have condemned the installation of the system.
However, there is no sign that Thaad was used against the missile tested on Sunday.
Newly-installed South Korean President Moon Jae-in, who is seeking deeper engagement with the North, has convened an urgent meeting of his national security council in response.