Pyongyang, North Korea - Russian President Vladimir Putin on Wednesday signed a mutual defense agreement with North Korea's Kim Jong-un, who offered his "full support" for the war on Ukraine.

The pledge of military cooperation was part of a strategic treaty signed during a summit in Pyongyang, where Putin was making his first visit in 24 years.

"It is really a breakthrough document," Putin said at a press conference in the North Korean capital, adding that it provided, "among other things, for mutual assistance in case of aggression against one of the parties to this treaty," Russian news agencies reported.

The two countries have been allies since North Korea's founding after World War II, and have drawn even closer after Russia's invasion of Ukraine in 2022 isolated Putin on the global stage.

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The US and its allies, which slammed the summit, have accused North Korea of providing weapons to Russia for its war in Ukraine.

Putin said Russia "does not rule out military-technical cooperation with the DPRK in connection with the treaty that was signed today."

Kim called the Russian leader the "dearest friend of the Korean people" and said his country "expresses full support and solidarity to the Russian government" over the war in Ukraine, which has triggered rafts of UN sanctions on Moscow.

Putin, in turn, thanked his host Kim, saying Moscow appreciated the "consistent and unwavering" support.

The two heavily sanctioned countries would not tolerate Western "blackmail," and Putin called for a review of UN sanctions on North Korea.

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"The indefinite restrictive regime inspired by the US and its allies at the UN Security Council towards the DPRK should be reviewed," Putin said.

Putin arrived in Pyongyang before dawn on Wednesday to be greeted by Kim on a red carpet at the airport where the pair embraced and smiled.

They then attended a welcoming ceremony in Kim Il-sung square, featuring a military band and mass synchronized dancing, after which Putin invited his host to visit Moscow.

The summit, which included a lengthy one-on-one chat between the leaders, was their second meeting in a year after Kim visited Russia in September.