North Korea launched several short-range ballistic missiles into its eastern sea Thursday in what South Korea is calling a “clear act of provocation.” 

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

The agency said multiple missiles were launched from an area around North Korea’s eastern port city of Wonsan from about 8:10 to 9:20 a.m. local time Thursday, with the farthest traveling about 497 miles. 

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. 

A missile flies during what North Korean state media said was a test of a new intermediate-range hypersonic ballistic missile at an undisclosed location on Jan. 6. (Reuters/KCNA)

Those launches come after South Korean and U.S. forces began their annual Freedom Shield exercise. 

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. 

In this undated photo provided on Wednesday, May 7,  by the North Korean government, North Korean leader Kim Jong Un, right, visits a munitions factory in North Korea.  (Korean Central News Agency/Korea News Service via AP)

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, the AP reported. 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. 

The Associated Press contributed to this report.