North Korea on Thursday fired various types of short-range ballistic missiles into its eastern sea, South Korea’s military said, adding to a run in military displays that raised animosities in the region. South Korean military officials were analyzing whether the tests were linked to the North’s weapons exports to Russia during its war in Ukraine.

South Korea’s Joint Chiefs of Staff said multiple missiles were launched from the area around the eastern port city of Wonsan from about 8:10 to 9:20 a.m., with the farthest traveling about 800 kilometers (497 miles). It didn’t immediately confirm the exact number of the missiles it detected.

Lee Sung Joon, spokesperson for the Joint Chiefs, said in a briefing the North Korean launches were possibly intended to test the performance of weapons it plans to export, as the country continues to send military equipment and troops to fuel Russia’s warfighting against Ukraine.

Lee said the tests likely involved a short-range ballistic missile system launched from vehicles — possibly modeled after Russia’s Iskander missile — and also large-caliber rocket artillery systems, which experts say blur the line between traditional artillery and ballistic systems due to their self-propulsion and guided flight.

The Joint Chiefs said South Korean and U.S. intelligence authorities detected the launch preparations in advance and tracked the missiles after they were launched. The countries were sharing the launch information with Japan, the Joint Chiefs said. It issued a statement denouncing the launches as a “clear act of provocation” that threatens peace and stability in the region.

Japanese Defense Minister Gen Nakatani told reporters that none of the North Korean missiles reached Japan’s exclusive economic zone and there was no damage to vessels or aircraft in the area. Nakatani said Japan’s government “sternly protested and strongly condemned” the launches through the North Korean embassy in Beijing.

It was the North’s first known ballistic activity since March 10, when it fired several ballistic missiles hours after U.S. and South Korean troops began an annual combined military exercise, and the country’s sixth launch event of the year.

Tensions on the Korean Peninsula have escalated in recent months as North Korean leader Kim Jong Un continues to accelerate the development of his nuclear and missile program and supply weapons and troops to support Russia’s war against Ukraine.

Thursday’s launch came a day after North Korean state media said Kim urged munition workers to boost the production of artillery shells amid his deepening alignment with Moscow.

After denying its war involvement for months, North Korea last month confirmed for the first time that it had sent combat troops to help Russia in recapturing parts of the Kursk region, which had fallen to a surprise Ukrainian incursion last year. Moscow also acknowledged the North Korean involvement, with Russian President Vladimir Putin issuing a statement thanking the North for sending troops to support his forces and promising not to forget their sacrifices.

Recent South Korean intelligence assessments suggest that North Korea has sent about 15,000 soldiers to Russia, and that nearly 5,000 of them have been killed or injured while fighting against Ukrainian forces. Washington and Seoul have also accused North Korea of supplying Russia with various types of military equipment, including artillery systems and shells and ballistic missiles.

Analysts say North Korea’s official acknowledgment of its military support for Russia is likely aimed at cementing a deeper, long-term partnership with Moscow and securing greater compensation, potentially including advanced military technology that could enhance the threat posed by Kim’s nuclear-armed forces.

By formalizing its role as a participant in the war, North Korea may also be positioning itself to seek compensation in future negotiations to end the conflict in Ukraine, according to a recent report by the Institute for National Security Strategy, a think tank affiliated with South Korea’s intelligence agency.

South Korea says North Korea has fired several missiles toward its eastern waters