Russian President Vladimir Putin spoke to North Korean leader Kim Jong Un reiterating that the two countries will "expand the comprehensive and constructive bilateral relations with common efforts," Pyongyang's state media reported Monday.

In a letter to Kim for Korea's liberation day, Putin said closer ties would be in both countries' interests and would help strengthen the security and stability of the Korean peninsula and the Northeastern Asian region, North Korea's KCNA news agency said.

Kim also sent a letter to Putin saying Russian-North Korean friendship had been forged in World War II with victory over Japan, which had occupied the Korean peninsula.

The "strategic and tactical cooperation, support and solidarity" between the two countries have since reached a new level in their common efforts to frustrate threats and provocations from hostile military forces, Kim said in the letter. KCNA did not identify the hostile forces, but it has typically used that term to refer to the United States and its allies.

Kim predicted cooperation between Russia and North Korea would grow based on an agreement signed in 2019 when he met with Putin.

North Korea in July recognized two Russian-backed breakaway people's republics in eastern Ukraine as independent states, and officials raised the prospect of North Korean workers being sent to the areas to help in construction and other labor.

Ukraine, which is resisting a Russian invasion described by Moscow as a "special military operation," immediately severed relations with Pyongyang over the move.