NATO on Monday confirmed that North Korean troops have been sent to help Russia in its almost three-year war against Ukraine and said some have already been deployed in Russia’s Kursk border region, where Russia has been struggling to push back a Ukrainian incursion.

“Today, I can confirm that North Korean troops have been sent to Russia, and that North Korean military units have been deployed to the Kursk region,” NATO Secretary-General Mark Rutte told reporters.

Rutte said the move represents “a significant escalation” in North Korea’s involvement in the conflict and marks “a dangerous expansion of Russia’s war.”

Adding thousands of North Korean soldiers to Europe’s biggest conflict since World War II will pile more pressure on Ukraine’s weary and overstretched army. It will also stoke geopolitical tensions in the Korean Peninsula and the wider Indo-Pacific region, including Japan and Australia, Western officials say.