SEOUL, June 18, 2024 (BSS/AFP) - Russian President Vladimir Putin on Tuesday praised North Korea for "firmly supporting" Moscow's war in Ukraine ahead of his visit to Pyongyang aimed at boosting ties between the nuclear-armed allies.

"We highly appreciate that the DPRK (North Korea) is firmly supporting the special military operations of Russia being conducted in Ukraine," Putin wrote in an article carried by the official Korean Central News Agency.

The two countries are "now actively developing the many-sided partnership," Putin wrote, pointing to, for example, the fact that Moscow and Kim Jong Un's regime have been "maintaining the common line and stand at the UN."

Putin is set to arrive in the isolated North, which is under successive rounds of United Nations sanctions over Kim's banned weapons programs, late Tuesday for his first visit since 2000.

The trip "will put bilateral cooperation onto a higher level with our joint efforts and this will contribute to developing reciprocal and equal cooperation between Russia and the DPRK," the Russian leader wrote, according to KCNA.

Historic allies dating back to North Korea's founding after the second world war, Moscow and Pyongyang have drawn ever closer since Russia's invasion of Ukraine in 2022, as Putin has become increasingly isolated and is looking for friends, experts say.

Last year, Kim made a rare overseas trip on his bulletproof train to meet Putin at a Russian spaceport.

Seoul, Washington and Kyiv have subsequently claimed North Korea is shipping weapons to Russia for use in its war in Ukraine, violating rafts of UN sanctions, in return for technical help with its nascent satellite programme.

North Korea has denied this, calling the claim "absurd" -- even as it thanked Russia for using its UN veto in March to effectively end monitoring of sanctions violations, just as the UN experts were starting to probe alleged arms transfers.

Kim has also ramped up weapons testing, including a flurry of launches this year of cruise missiles, which analysts said North Korea could be supplying to Russia for use in Ukraine.

A Pentagon report last month said Russia was using North Korean ballistic missiles in Ukraine, citing debris analysis.

- Defence cooperation -

Citing a Kremlin aide, Russian agencies said Monday the two leaders will sign "important documents" during the visit.

This may include a "comprehensive strategic partnership treaty" which will outline future co-operation and deal with "security issues", Kremlin aide Yuri Ushakov was quoted as saying by state-run Russian news agencies.

But experts said that in reality, any new agreements would be focused on boosting the two countries' defence cooperation.

"Moscow and Pyongyang want to leverage the perception that their ties are long term and increasingly integrated regarding defense," Patrick Cronin, chair for Asia-Pacific Security at the Hudson Institute, told the Yonhap new agency.

"They may also suggest this relationship is comprehensive. Certainly both countries are facing serious economic dilemmas. But regardless of the words used, current relations will focus on defense cooperation."

Putin's trip to the North is in reality "two strongmen with weak economies basking in the limelight as leaders to swap military technology and subvert the US-led order," Cronin told Yonhap.