North Korea's UN ambassador has denounced the security cooperation among Japan, the United States and South Korea, calling it a military alliance resembling NATO.

Ambassador Kim Song addressed the United Nations General Assembly on Tuesday.

He said, "The formation of the tripartite military alliance among the US, Japan and the 'Republic of Korea' has put into practice its long-sought ambition for 'Asian version of NATO,' thus introducing a 'new cold war' structure to Northeast Asia."

Kim also hit back at earlier remarks made by South Korean President Yoon Suk-yeol at the General Assembly in which he condemned North Korea and Russia for pursuing military cooperation.

Kim said the development of equal and reciprocal relations between and among independent sovereign states is not an issue for the "Republic of Korea" to interfere in "as it is no more than a colony of the US."

Observers say Kim's usage of South Korea's official name could be interpreted as a sign that Pyongyang officially views it as a different country now.

The ambassador said, "the military security situation in and around the Korean Peninsula was driven closer to the brink of a nuclear war."

Kim added that his country must accelerate the buildup of its self-defense capabilities to impregnably defend itself.