Sunday's missile test is the first of 2017, the first of Trump's presidency, and comes amid a review of North Korea policy by the new USA administration.
Meanwhile, the Japanese government confirmed the North's missile test and South Korea's presidential office called a national security meeting.
North Korea's latest ballistic missile test was, to a certain degree, expected, a US official revealed. Just think when the North does finally deploy a long-range ICBM that can reach America.
Sunday's launch comes as Japanese Prime Minister Shinzo Abe and U.S. President Donald Trump continued talks in Florida during Abe's first state visit to the U.S. since Trump's January 20 inauguration.
Both South Korean and American officials are closely monitoring the situation, while President Trump has also been briefed about the test.
The nuclear tests, two of which were conducted in 2016, sparked global condemnation and raised concerns that North Korea was moving towards its goal of a nuclear-armed missile that could one day be capable of striking the USA mainland.
It appears that North Korea and its missile testing may have been influenced by the political drama unfolding in the United States.
A spokesman for U.S. Strategic Command said assessments were under way as to the type of missile and other details. The remarks elicited a searing response from Mr Trump, who said "it won't happen".
Inada told reporters that her ministry will make every effort to find out more about the launch as well as conduct surveillance and warning activities. Yonhap reported that while determinations are still being made, it was not believed to be an intercontinental ballistic missile capable of reaching the US mainland.
His comments prompted a vow of an "overwhelming" response from US Defence Secretary James Mattis, when he travelled to South Korea earlier this month.
General James "Mad Dog" Mattis reassured South Korea the United States would continue its support amid increasing fears over North Korea's nuclear capabilities.
They assessed the now urgent security situations, including the DPRK's nuclear and missile programs, vowing to further build up a joint defense posture against Pyongyang.
Technical details aside, this test is significant for being the first significant North Korean provocation for the new US administration.
The Trump administration is expected to exert pressure on North Korean ally China to rein in Pyongyang's nuclear ambitions, but Beijing has maintained all along that dialogue is key to resolving the issue.