The latest in an unusual number of missile tests this year, two ballistic missiles were launched by North Korea on Friday toward the ocean off its east coast, according to the South Korean military.

Only a few days after launching two more missiles and a day after charges that it was supplying weapons to Russian forces in Ukraine, North Korea resumed its destabilizing behavior, according to its neighbors.

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.”

The Wagner Group was allegedly supplied with weapons by North Korea, according to Canada, which said the supply “obviously violates international law and United Nations Security Council resolutions.”

A story in the Japanese media about ammunition shipments to Russia was also refuted by Pyongyang’s foreign ministry on Friday, calling it “groundless.”

According to Tokyo Shimbun, additional shipments from North Korea are anticipated in the upcoming weeks. Last month, the country sent artillery shells and other supplies to Russia by rail.

Without mentioning Wagner, the foreign ministry of North Korea claimed that it has never exchanged armaments with Russia and chastised Washington for supplying Ukraine with deadly weapons.