Russian President Vladimir Putin will travel to North Korea on Tuesday, in a rare visit that may see Moscow sign a "strategic partnership treaty" with Pyongyang, the Kremlin said.
The historic trip -- which the Kremlin called a "friendly state visit" -- comes as Putin seeks ammunition for his military offensive in Ukraine and as the West suspects Pyongyang of sending weapons to Moscow.
"Several documents will be signed," among which will be "important, highly significant documents", Kremlin aide Yuri Ushakov was quoted as saying by state-run Russian news agencies.
This may include a "strategic partnership" document that will be an updated version of a 1961 Soviet-era agreement and one signed when Putin last visited the reclusive state in 2000, he said.
The document will be changed to adapt to a "deep evolution of the geopolitical situation in the world and the region", Ushakov said.
Russia is now, along with North Korea, one of the most heavily sanctioned countries in the world and Moscow has spent months warming its relations with Pyongyang as it faces isolation in the West.
NATO chief Jens Stoltenberg said Putin's visit showed how "dependent" Moscow was on authoritarian leaders to wage its offensive in Ukraine.
Ukraine's Foreign Minister Dmytro Kuleba dismissed the "lonely bromance" between Putin and North Korean leader Kim Jong Un, calling for more Western air defence systems and weapons.
"The best way to respond to it is to continue strengthening the diplomatic coalition for just and lasting peace in Ukraine and delivering more Patriots and ammunition to Ukraine," Kuleba told AFP.
Western countries have accused North Korea of sending weapons to Russia for use in Ukraine, which Moscow and Pyongyang have denied. Kyiv has said it has found North Korean shells on the battlefield.
Moscow said Putin will arrive in Pyongyang on Tuesday evening, where he will attend a concert in his honour, before signing "important" documents with Kim on Wednesday.
The Kremlin chief will be taking a large delegation including his foreign, defence, health, transport and space ministers, and may speak to the press along with Kim, Ushakov said.
- Soviet-era ties -
Washington and Seoul say Russia has provided Pyongyang with technical help for its satellite programme and sent aid to the food-strapped state.
The trip comes nine months after Putin hosted Kim on a rare foreign trip in the Russian Far East where the pair lavished each other with praise.
Russia and North Korea, which share a small land border, have historic links since the Soviet Union helped found the tiny state after the Korean War in the 1950s.
Since the fall of the USSR, Russia was one of the few countries to have working relations with Pyongyang.
It will be Putin's second visit to the country in his time in power, following a trip 24 years ago shortly after becoming president, to meet Kim Jong Un's father Kim Jong Il.
Back then, Putin was a frequent traveller, regularly touring the United States and Europe.
Now Russia finds itself under heavy international sanctions and the Kremlin leader is a persona non grata in most of the Western world, officially wanted by the International Criminal Court.
Moscow said Putin will travel on to Vietnam from North Korea.
- 'Comrades-in-arms' -
Kim said last week that ties with Russia had "developed into an unbreakable relationship of comrades-in-arms".
When the leaders saw each other in September, Putin said he saw "possibilities" for military cooperation with North Korea, while Kim wished the Kremlin chief "victory" in Ukraine, with the two symbolically gifting each other rifles.
The Kremlin had for months promised Putin will reciprocate a visit and made increasingly praising statements on North Korea.
In March, Russia used its UN Security Council veto to effectively end UN monitoring of North Korean sanctions violations, a move seen as a victory for Pyongyang.
Russia and North Korea have denied that Pyongyang's weapons are being used in Ukraine.
But in May, South Korea said its northern rival fired multiple short-range ballistic missiles, with some experts saying they could be tests for weapons destined for use against Ukraine.
As the Kremlin and Pyongyang have publicly deepened their ties, Moscow's relationship with South Korea has become hugely strained.
Seoul is a major weapons exporter to Kyiv. President Yoon Suk Yeol last month promised to maintain its support in a phone call with Ukrainian counterpart Volodymyr Zelensky.
South Korea last month announced separate sanctions on Russian and North Korean individuals and companies allegedly trading military supplies.