SEOUL (Reuters) - Russian President Vladimir Putin and North Korean leader Kim Jong Un agreed to develop their nations' relations, which have emerged a strategic fortress, during a meeting on the first day of Putin's visit to Pyongyang on Wednesday, North Korean state media.

Kim greeted Putin at dawn at Pyongyang airport, shaking hands, embracing and talking beside the Russian leader's plane. The pair then rode in the same limousine and walked together into Putin's hotel.

Putin made his first visit to North Korea in 24 years vowing to deepen trade and security ties with the reclusive nuclear-armed state and to support it against the United States.

The meeting between the two leaders demonstrates "invincibility and durability" of friendship and unity between North Korea and Russia, according to state news agency KCNA.

North Korea- Russia relations have "emerged as a strong strategic fortress for preserving international justice, peace and security and an engine for accelerating the building of a new multi-polar world," KCNA said.

Officials in Washington and Seoul say North Korea has supplied weapons to Russia to help it fight in Ukraine.

Moscow and Pyongyang have denied arms transfers but have vowed to boost military ties, possibly including joint drills.

(Reporting by Ju-min Park and Josh Smith; Editing by Stephen Coates)