The US Pacific Command said it was monitoring the situation and consulting with allies after North Korea launched ballistic missiles, adding that Pyongyang's missile launch "underscores the threat that its illegal weapons program poses to its neighbors and the international community."
CNN quoted a high-ranking US official as confirming that North Korea fired two short-range ballistic missiles in the early hours of Thursday, according to intelligence assessments.
The National Security Council in South Korea expressed grave concern over the move taken by the northern neighbor.
For his part, the Japanese Prime Minister said that Pyongyang's launch of two ballistic missiles "constitutes a threat to the security of Japan and the region."
This is the first such test reported since US President Joe Biden took office on January 20, noting that North Korea's launching of ballistic missiles is prohibited under UN Security Council resolutions.
In turn, the South Korean Joint Chiefs of Staff said that at least two "unspecified type projectiles" were launched into the sea from South Hamgyeong Province on the northeastern coast of Korea.
The agency added in a statement that South Korean and American intelligence agencies are analyzing the launch data, in order to obtain additional information.
The Japanese Coast Guard had previously warned ships not to approach any objects that fell, and instead asked them to provide them with any information related to the incident.
US and South Korean officials said that North Korea fired two short-range missiles on Sunday, but Biden played down the test, saying it was "normal business."
Officials in Washington said they were still ready for dialogue.