North Korea fired two ballistic missiles toward the sea off its east coast on Friday, the South Korean military said, the latest in an unprecedented number of missile tests this year.
Coming only days after two other missiles were launched and a day after allegations were made the country is shipping munitions to Russian forces in Ukraine, North Korea continued actions its neighbours say are destabilising the region.
South Korea's Joint Chiefs of Staff said the missiles flew 350 km (217.5 miles) and 250 km, respectively, after being fired at around 4:30 p.m. (0730 GMT) from the Sunan area of the North Korean capital Pyongyang. Japan's coast guard also reported a suspected ballistic missile launch.
Such launches are a "serious provocation that harms peace and stability" on the Korean peninsula and beyond and a clear violation of U.N. resolutions, South Korea's military said, urging an immediate halt.
"We will track and monitor developments together with the United States in preparation for additional provocations by North Korea, while maintaining a firm readiness posture based on our ability to overwhelmingly respond to any provocations by North Korea," the Joint Chiefs of Staff said in a statement.
Japan's State Minister of Defence Toshiro Ino said Tokyo has lodged a strong protest to North Korea through diplomatic channels in Beijing.
Japanese Chief Cabinet Secretary Hirokazu Matsuno condemned the latest launch as "absolutely unacceptable."
"North Korea's rapid escalation of provocations in a series of actions threatens the peace and security of Japan's region and the international community," Matsuno told reporters.
The U.S. military said the launch did not pose an immediate threat to U.S. personnel or territory, or its allies, but said the action highlights the "destabilizing impact" of Pyongyang's nuclear and ballistic missile programs.
The launch comes five days after the isolated country fired two mid-range missiles in what it called an "important" test for the spy satellite programme it intends to complete by April.
The White House said on Thursday that North Korea completed an initial arms delivery of infantry rockets and missiles to a private Russian military company, the Wagner Group, to shore up Russian forces in Ukraine.
Wagner owner Yevgeny Prigozhin denied the assertion as "gossip and speculation."
Canada on Friday levelled its own charges that North Korea had supplied the Wagner Group with weapons, saying the delivery "clearly violates international law and United Nations Security Council resolutions."
Pyongyang's foreign ministry on Friday also denied a Japanese media report on munitions shipments to Russia, calling it "groundless".
Tokyo Shimbun said North Korea had shipped artillery shells and other munitions to Russia by train last month, with additional shipments expected in coming weeks.
North Korea's foreign ministry said it has never conducted arms transactions with Russia and criticised Washington for giving lethal weapons to Ukraine, with no mention of Wagner.
(Reporting by Hyonhee Shin and Jack Kim; Additional reporting by Mariko Katsumura, Chang-Ran Kim and Kantaro Komiya in Tokyo; Editing by Tomasz Janowski and Rosalba O'Brien)