The United Nations and the Pentagon have condemned North Korea's latest missile test, calling it a "further troubling violation" of Security Council resolutions.
UN Secretary-General Antonio Guterres denounced the ballistic missile firing, saying: "The DPRK leadership must return to full compliance with its international obligations and to the path of denuclearisation."
The UN Security Council was scheduled to hold an emergency meeting on Tuesday (NZ time) on North Korea's missile launch on Monday.
The Pentagon has also strongly condemned North Korea's latest missile test, adding that the United States' commitment to protect the homeland and allies such as Japan and South Korea was "ironclad".
"We are capable of defending against a North Korean ballistic missile attack and will take all necessary measures to deter and defeat threats to our and our allies' territories and citizens," Pentagon spokesman Captain Jeff Davis told reporters.
North Korea announced it had successfully test-fired a new type of medium- to long-range ballistic missile the previous day, claiming advances in a weapons program it is pursuing in violation of UN resolutions.
An unidentified projectile was fired into the sea off the east coast of the Korean peninsula, the South Korean military says.
The object was launched early on Sunday from an area in North Korea's western region, the South's Office of the Joint Chiefs of Staff said in a short statement. It did not provide further details.
Earlier, the country's Yonhap news agency reported in a short dispatch that the North had fired a ballistic missile.
North Korean leader Kim Jong Un said in his New Year speech that the country was close to test-launching an intercontinental ballistic missile (ICBM) and state media have said such a launch could come at any time.
That prompted a vow of an "overwhelming" response from US Defense Secretary James Mattis when he travelled to South Korea earlier this month.
North Korea has conducted two nuclear tests and a number of missile-related tests at an unprecedented rate since early last year and was seen by experts and officials to be making progress in its weapons capabilities.