The Russian and North Korean governments have decided to open direct monthly flights in a bid to strengthen bilateral ties.
The first direct flight from Moscow to Pyongyang since the mid-1990s was set to depart on Sunday evening.
While both nations are taking steps to improve their relations with each other, the rival countries, including South Korea and Ukraine, are expressing concern over what they see as only aimed at strengthening military ties between Moscow and Pyongyang.
The eight-hour, 6,500-kilometre (4,040-mile) flight, operated by private Russian carrier Nordwind Airlines, was due to take off from Moscow's Sheremetyevo Airport at 19:00 local time (18:00 CEST).
Kyiv and South Korean intelligence have accused North Korea of supplying Russia with artillery and ballistic missiles to strike Ukraine while reinforcing Russian fronts with more than 10,000 troops to help repulse a Ukrainian incursion into Russia's Kursk region.
The direct flights are considered a significant stride in cooperation, as both nations can now directly transport military weapons to the front lines against Ukraine.
Besides, the Russian government said on Sunday that its annual navy parade to be held in St. Petersburg was cancelled for unspecified "security reasons."
In a televised message, Russian President Vladimir Putin praised the "courage" and "heroism" of Russian marines involved in the war of aggression against Ukraine since February 2022.
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Meanwhile, in a separate development, the North Korean side also rejected a call for dialogue from the South Korean government on Monday.
Kim Yo Jong, sister of North Korean leader Kim Jong Un and vice department director of the Central Committee of the Workers' Party, stated in the state-run media on Monday.
In a harshly worded statement, Kim’s sister directly addressed the Seoul administration, saying, "No matter what policy is adopted and whatever proposal is made in Seoul, we have no interest in it and there is neither the reason to meet nor the issue to be discussed.”