SEOUL, South Korea (AFP) — South Korea “won’t sit idle” over the North’s deployment of thousands of troops to help Russia fight Ukraine, President Yoon Suk Yeol said Thursday, slamming it as a “provocation.”

Yoon made the remark after talks with visiting Polish President Andrzej Duda, adding that the two countries agreed North Korea’s deployment was “a provocation that threatens global security beyond the Korean Peninsula and Europe.”

Poland’s Duda spoke to Yoon on Thursday, after which the two leaders “strongly condemned North Korea’s nuclear and missile development and provocations, as well as its illegal military cooperation with Russia.”

Seoul’s spy agency has said that around 3,000 North Korean soldiers are currently in Russia training, likely to deploy to the frontlines against Ukraine soon, with thousands more troops to be sent by December.

The North Atlantic Treaty Organization and Washington have confirmed that Pyongyang’s soldiers are now training in Russia, warning that if they were to join the fight against Kyiv, it could mark a dangerous escalation of the grinding war.

South Korea, one of the world’s top 10 weapons exporters, has long resisted calls from its allies including Washington to supply Kyiv with weapons, pointing to long-standing domestic policy which bars Seoul from selling weapons to actors engaged in active conflicts.

It has recently hinted that it could look at reviewing this policy in light of North Korea’s actions, and Yoon said Thursday that Seoul would “take necessary actions in cooperation with the international community” to respond.

Meanwhile, Russian lawmakers voted unanimously on Thursday to ratify a defense treaty with North Korea that provides for “mutual assistance” if either party faces aggression.

Lawmakers in the lower house State Duma voted 397 to 0 to ratify the treaty, which will be now sent to the upper Federation Council for their approval.

Both houses of parliament act as rubber stamps for the Kremlin.

Russian President Vladimir Putin signed the defense treaty on a visit to Pyongyang in June, but many details remain unclear, including whether Pyongyang would be covered by Moscow’s nuclear umbrella.