China is North Korea's most important ally, although relations have at times been strained by Pyongyang's nuclear programme.

North Korea is expected to stage a massive military parade on Friday, showcasing its latest advanced weaponry, including intercontinental ballistic missiles (ICBMs).

South Korea's military said the North appeared to have been conducting "rehearsals mobilising equipment and missiles" and that there was a "high chance" that the parade will be held Friday night.

"North Korea is expected to get about 1mm of rain per hour starting late afternoon, so the parade should still be possible -- though the weather may affect any planned air power displays," a defence ministry official told reporters.

The celebrations come as Kim has been emboldened by the war in Ukraine, securing critical support from Russia after sending thousands of North Korean troops to fight alongside Moscow's forces. Russia's former president Dmitry Medvedev, deputy head of its Security Council, is attending this week's anniversary celebrations.

Kim praised Li's visit as "showing the invariable support and special friendly feeling towards the WPK and the government and people of the DPRK", using acronyms for North Korea's ruling party and official name.

He also lauded Beijing's efforts to maintain "traditional DPRK-China friendly and cooperative relations and further develop them", state news agency KCNA reported.

- 'Powerful beings' -

Last month, Kim appeared alongside Chinese President Xi Jinping and Russian leader Vladimir Putin at an elaborate military parade in Beijing.

North Korea held mass games and art performances at May Day stadium in Pyongyang Thursday, where Kim made a speech with high-level foreign guests, including Medvedev and Vietnam's Communist Party chief To Lam, in attendance.

"Today our people are standing in front of the world as powerful beings who know no insurmountable difficulties and no unachievable cause," Kim said in the speech.

The celebrations in Pyongyang come after Seoul said a meeting between North Korea and the United States "cannot be ruled out" on the sidelines of this year's APEC summit in South Korea.

US President Donald Trump met Kim three times during his first term and once famously said the pair had fallen "in love", but he ultimately failed to secure a lasting agreement on North Korea's nuclear programme.

Since then Pyongyang has repeatedly declared itself an "irreversible" nuclear state.

In a joint statement from Moscow and Pyongyang released by KCNA Thursday, Russia's ruling party said it "expressed firm support for the measures taken" by North Korea "to bolster up the country's defence capabilities".

"Kim's greatest concern is how to assure the continued survival and the international acceptance of his regime," Sergey Radchenko, professor at the Johns Hopkins University, told AFP.

"So in this sense, a multi-vector diplomacy that includes China, in addition to Russia, makes sense."