Putin enjoys red carpet welcome in North Korea

The United States and its allies have accused North Korea of providing ammunition and missiles to Russia for its war in Ukraine, and there are worries Putin's visit will lead to further military deliveries.

Putin said at the start of Wednesday's talks a "new foundation document" was ready to be signed that would set the framework for relations in the long term, as Kim spoke glowingly of the allies' ties.

"Relations between our countries are entering a new era of blossoming, which cannot be compared even with the period of Korean-Soviet relations of the last century," Kim said, according to Russian news agencies.

The summit is their second meeting in a year, after Kim took his bulletproof train to Russia's far east last September for a summit with Putin at a space port.

Experts have warned the trip is likely to focus on defence ties, although the leaders are expected to publicly highlight cooperation in the economic sector as any arms deals would violate United Nations Security Council resolutions banning Pyongyang's nuclear and ballistic missile programs.

"Russia requires North Korea's weapon support due to the prolonged war in Ukraine, while North Korea needs Russia's support in terms of food, energy, and advanced weapons to alleviate the pressure from sanctions," Koh Yu-hwan, North Korean studies emeritus professor at Dongguk University told AFP.

"The military alliance aspect, however, should be viewed separately from what is publicly announced and what is actually discussed in the meetings between the two leaders," he said, adding Moscow was cautious about "completely burning bridges with countries like South Korea."

 'Arsenal for autocracy' 

Pyongyang has described allegations of supplying weapons to Russia as "absurd".

However, it thanked Russia in March for using its Security Council veto to effectively end monitoring of sanctions violations just as UN experts were starting to probe alleged arms transfers.

The United States voiced "concern" Monday about Putin's trip over the security implications for South Korea as well as Ukraine.

The two Koreas have remained technically at war since their 1950-53 conflict and the border dividing them is one of the most heavily fortified in the world.

Highlighting those security concerns, South Korea said its troops fired warning shots at soldiers from the North who briefly crossed the border Tuesday and then retreated.

This week's visit is a way for Putin to thank the North "for acting as an 'arsenal for autocracy' in support of his illegal invasion of Ukraine," said Leif-Eric Easley, a professor at Ewha University in Seoul.

It is also part of Russia's drive to secure "strategic space" in Northeast Asia to counter US influence in the region, Seoul-based Institute for National Security Strategy's senior research fellow Kim Sung-bae told AFP.

"This intention is further evidenced by Putin's visit to Vietnam," he said, with the Russian leader set to fly to Hanoi after his trip to the North.