North Korea fired at least two ballistic missiles, its third test in less than two weeks, just hours after criticising a US push for new sanctions over the previous launches as a "provocation" and warning of a strong reaction.

South Korea's National Security Council held an emergency meeting and expressed "strong regret" over the test and called on Pyongyang to return to talks.

"It emphasised that North Korea's series of missile tests are not helpful for stabilising the situation of the Korean peninsula at this important time, and urged North Korea to swiftly respond to calls for dialogue," the presidential Blue House said in a statement.

South Korea's Joint Chiefs of Staff (JCS) said it hadd etected what it presumed were two short-range ballistic missiles (SRBMs) launched eastward from Uiju, in North Pyongan province on the North's west coast, near its border with China.

Japan's coast guard also said the North fired what could be a ballistic missile.

The missiles appeared to have landed in the sea outside Japan's exclusive economic zone, broadcaster NHK said, citing an unnamed Japanese defence ministry official.

Despite international sanctions over its nuclear weapons programme, Pyongyang tested what it said were hypersonic missiles on 5 January and 11 January.

"The actions of North Korea, including the repeated ballistic missile launches, are a threat to the safety of our nation and the region, and they are an important issue for all of international society," Hirokazu Matsuno, Japan's chief cabinet secretary, told a regular news conference.

The US military's Indo-Pacific Command said while it assessed that the launch did not pose an immediate threat to the United States or its allies, it highlighted the "destabilising impact of the (North's) illicit weapons programme."

The two missiles travelled about 430km to a maximum altitude of 36km, South Korea's JCS said.

In contrast to today's tests, each of the earlier launches involved a single missile fired from Jagang province, neighbouring North Pyongan.

North Korea defended the missile tests as part of its legitimate right to self-defence and said the United States was intentionally escalating the situation with new sanctions, state media said, citing the foreign ministry.

The North's recent development of a "new type" weapon was just part of efforts to modernise its national defence capability, and did not target any specific country or harm the security of neighbours, the ministry said in a statement on the KCNA state news agency.

The statement warned of an unspecified "stronger and certain reaction" if the United States adopted a confrontational stance.

President Joe Biden's administration imposed its first sanctions on Wednesday over North Korea's weapons programmes following the series of missile launches.

It also called on the United Nations Security Council to act against several North Korean individuals and entities accused of violating security council resolutions that ban North Korea's missile and nuclear weapons development.

US Secretary of State Antony Blinken said the United States had made clear it had no hostile intent toward North Korea and was willing to engage in talks without preconditions, but the tests were "profoundly destabilising."

The North Korean foreign ministry said that while Washington may talk of diplomacy and dialogue, its actions showed it was still engrossed in its policy for "isolating and stifling" the North.