South Korean Ambassador to Russia Lee Do-hoon voiced alarm over increasing military cooperation between North Korea and Russia during his meeting with Andrey Rudenko, the Russian deputy foreign minister in charge of the Asia-Pacific region, on Wednesday, the Foreign Ministry in Seoul said Thursday.

The meeting, which Seoul described as an opportunity to hear Russia's stance on the "Comprehensive Strategic Partnership Treaty" signed by President Vladimir Putin and North Korean leader Kim Jong-un, marked their first encounter in Moscow since Putin's visit to Pyongyang on June 19.

"During the meeting, Ambassador Lee expressed our grave concerns regarding the treaty between Russia and North Korea, emphasizing that any cooperation aiding North Korea's military buildup poses a serious threat to our security," South Korea's Foreign Ministry said.

Lee also "requested a clear explanation from the Russian side on the matter."

The Foreign Ministry said the Russian side "expressed regrets over the Korean side's response" to Putin's visit to North Korea and clarified that "the treaty is of defensive nature, applicable only in the event of invasion while explaining relevant clauses of the treaty."

Seoul said both sides "agreed to continue necessary dialogue" regarding Putin's visit to North Korea and the treaty based on the meeting.

In a separate statement, the Russian Foreign Ministry on Wednesday said Rudenko urged South Korea to reconsider its "confrontational course, which essentially provokes an escalation of the situation on the peninsula."

On the same day, Russia's Foreign Ministry spokesperson Maria Zakharova issued another warning to Seoul regarding its announcement about reconsidering its position on the supply of lethal weapons to Kyiv, a move that followed the Putin-Kim summit.

"We would like to warn South Korea against taking ill-thought-out actions that could lead to irreversible consequences for Russia-South Korea relations," Zakharova said, according to Russia's state-run TASS news agency.

In direct response, South Korea's Foreign Ministry spokesperson Lim Soo-suk on Thursday said, "We warn the Russian side against making mistakes that could lead to irreversible consequences for Russia-Korea relations."

"We also hope that Russia will act in accordance with its status as a permanent member of the UN Security Council, breaking away from its reliance on North Korea," Lim added.

Minutes before releasing the outcome of the meeting between Lee and Rudenko, the South Korean government notably announced a new set of unilateral economic sanctions on Thursday, directly in response to the North Korea-Russia treaty.

Seoul has designated for sanctions five entities from Russia, North Korea and third-party countries, four Russian-flagged vessels and eight North Korean individuals involved in illegal activities, including weapons transport between Russia and North Korea, the import of refined petroleum into North Korea and North Korea's nuclear and missile development. The new set of sanctions are to take effect from Monday.