The top nuclear envoys of South Korea and the United States on Thursday pledged to resolutely counter the continuing illicit military cooperation between Russia and North Korea, emphasizing bilateral alignment and close coordination with the international community.

South Korean Special Representative for Korean Peninsula Peace and Security Affairs Kim Gunn, and US Senior Official for North Korea Jung Pak, met in Seoul, two days after a publicly disclosed meeting between Russian President Vladimir Putin and the North Korean foreign minister in Moscow.

A meeting of envoys from South Korea, the US and Japan was set to occur after the bilateral talks. This trilateral meeting represents the first instance since October.

"Both sides agreed to resolutely respond to the illicit cooperation between Russia and North Korea, which poses a serious threat to international security, including the Korean Peninsula, in coordination with the international community," South Korea's Foreign Ministry said in a Korean-language statement.

"In this context, both sides shared assessments on the recent developments in relations between Russia and North Korea, including Foreign Minister Choe Son-hui's visit to Russia, and committed to engaging in close discussions on how to respond going forward."

Kim and Pak also recognized the international community's grave warning of the "illicit military cooperation between Russia and North Korea." This warning was conveyed through diplomatic efforts, including the joint statement issued by foreign ministers from nearly 50 countries and the European Union, addressing North Korea's transfer of ballistic missiles to Russia.

Choe's visit to Russia earlier this week has sparked concerns regarding the potential expansion of military cooperation between the two countries. Specifically, there are apprehensions about Russia procuring North Korean weapons to support its ongoing unprovoked invasion of Ukraine, a clear violation of multiple UN Security Council resolutions.

Kremlin Spokesman Dmitry Peskov on Wednesday said Moscow seeks to "boost relations in all areas, including sensitive ones" when asked if the two countries discussed military cooperation during Choe's trip.

During the meeting, Kim and Pak also jointly condemned North Korea for "persisting in aggressive statements and actions that escalate tensions on the Korean Peninsula."

In early January, North Korea fired around 350 shells toward the inter-Korean western maritime border over three consecutive days. Pyongyang conducted a test of what it claimed to be a solid-fuel intermediate-range ballistic missile equipped with a hypersonic warhead on Sunday, the same day Choe arrived in Russia.

Kim and Pak also noted that such belligerence came after North Korean leader Kim Jong-un's public declaration of "hostile relations between the two countries" during the leader's year-end party plenum. During Monday's parliamentary meeting, Kim also directed the inclusion of his regime's objective of a full-scale occupation of South Korea in the event of war on the Korean Peninsula in the country's constitution.

"Both sides commit to firmly protect peace and stability on the Korean Penisula by sternly responding to any North Korean provocations and threats based on the ironclad South Korea-US alliance," the Foreign Ministry in Seoul said.

The South Korean and US envoys also "committed to actively exploring substantive measures to block key sources of funding for the North Korean regime," including illicit cyber activities, labor exports and maritime smuggling.

Kim Gunn also met his Japanese counterpart, Hiroyuki Namazu, director general for Asian and Oceanian affairs at the Japanese Foreign Ministry, on Wednesday afternoon and discussed a wide range of North Korean issues, including military cooperation between Moscow and Pyongyang and North Korean human rights violations that have been exacerbated due to North Korea's nuclear and missile developments.

Seoul and Tokyo also concurred on continuing to cooperate on humanitarian issues related to North Korea, including the problem of abductees and the protection of North Korean defectors, according to South Korea's Foreign Ministry.