North Korea fired a suspected ballistic missile towards its eastern sea on Saturday, the South Korean and Japanese militaries said, in its second launch this week.
South Korea's military said the North launched what was believed to be a submarine-launched ballistic missile (SLBM) into the sea off its east coast at around 0507 GMT from the area around the port city of Sinpo, where Pyongyang keeps submarines as well as equipment for test-firing such missiles.
The launch continues North Korea's recent streak of weapon demonstrations amid signs it is preparing for a nuclear test in the coming weeks or months.
Japanese Defence Minister Nobuo Kishi said the North's recent development in nuclear missile-related technology and repeated launches of ballistic missiles threatened the region and the international community.
"This is absolutely unacceptable," he told reporters.
Japan will continue to "strengthen defence capabilities drastically" to protect citizens from such threats, he said.
South Korea and Japan's militaries detected the North firing a suspected ballistic missile from near its capital, Pyongyang, on Wednesday.
The latest launch was probably North Korea’s 15th round of missile firings this year, including its first test of an intercontinental ballistic missile since 2017 that demonstrated potential range to reach the entirety of the United States.
It came three days before the inauguration of South Korean president-elect Yoon Suk Yeol, who has vowed to take a tougher approach over the North’s nuclear ambitions.
Experts say the unusually fast pace in testing activity underscores a brinkmanship aimed at forcing the United States to accept the idea of North Korea as a nuclear power and remove crippling sanctions. There are also signs Pyongyang is restoring tunnels at a nuclear testing ground in possible preparation for another detonation. It conducted its sixth and last nuclear test at the site in September 2017.
North Korean leader Kim Jong-un has punctuated his missile tests with statements warning the North could proactively use its nuclear weapons if threatened or provoked, which experts say possibly portends an escalatory nuclear doctrine that would create greater concerns for South Korea and Japan.
The South Korean and Japanese militaries said the North Korean missile fired on Wednesday travelled about 500 kilometres at a maximum altitude of 800km. North Korea's state media have yet to comment on the test.
With reporting from agencies.