North Korea fired what was believed to be a ballistic missile on Tuesday, the second within a span of days.
It comes after leader Kim Jong Un threatened more military advances in a New Year's speech.
The latest launch has already drawn fire from neighbors.
Japanese Prime Minister, Fumio Kishida:
“Under these circumstances, it is very regrettable that North Korea continues to launch missiles."
And South Korea's National Security Council expressed "strong regret" at an emergency meeting, saying the repeated offense risked destabilizing the region.
Officials added it’s cooperating with U.S. allies to closely monitor the situation.
The launch underscored Kim Jong Un's New Year promise to bolster the military, as peace talks with South Korea and the U.S. have stalled.
North Korea has said it is open to talk, but only if the U.S. and others drop "hostile policies" such as sanctions and military drills.
UN Security Council resolutions ban North Korea from all ballistic missile and nuclear tests and have imposed sanctions over the programs.