North Korean leader Kim Jong Un has reiterated his support for Russia amid the invasion of Ukraine, as Moscow celebrates its national holiday commemorating the declaration of the primacy of the Constitution of the Russian republic over the Soviet Union.

The ruling Workers' Party newspaper, Rodong Sinmun, reported on Sunday that Kim had sent a congratulatory message to Russian President Vladimir Putin for "Russia Day" celebrated on June 12.

The newspaper quoted Kim as saying that under Putin's leadership, Russia has overcome all difficulties in achieving the great feat of justice to protect its dignity and security.

Kim added that North Korean people give Russia their full support and cheers.

He went on to say he is confident that the strategic cooperation between the two countries will become even tighter to safeguard international justice and ensure global security.

Last month, Russia vetoed a UN Security Council sanctions resolution on North Korea over the country's repeated launches of ballistic missiles.