Kim Jong Un showed off North Korea's latest weapons to Russia's Defence Minister Sergei Shoigu on Wednesday.
Pyongyang invited the Russian delegation led by Mr Shoigu, as well as Chinese officials.
They will attend Pyongyang's celebrations of the 70th anniversary of the Korean War armistice, marked typically by massive military parades.
The weapons on display included the Hwasong intercontinental ballistic missile (ICBM).
Successfully tested in April, it is believed to be the country's first ICBM to use solid propellants, which makes it quicker to launch than liquid-fuel ones.
Also on show were two new drone designs, including one resembling the primary offensive strike drone used by the US Air Force, according to NK News, a specialist site focusing on North Korea.
Mr Shoigu's visit comes amid accusations that Pyongyang is supplying Russia with arms for use in its war in Ukraine - a claim that both Pyongyang and Moscow deny.
North Korea's KCNA news agency said Mr Kim and Mr Shoigu discussed "matters of mutual concern" in the fields of national defence and on the international security environment.
The delegations' visit for North Korea's Victory Day - as the 1953 end of hostilities is called in the North - is expected to finish on Thursday with an extensive military parade. The Koreans are technically still at war because no peace agreement was reached when the conflict ended.
Both Russia and China are long time allies of North Korea. Their visit marks the first time Mr Kim has thrown open the doors to foreign guests since the Covid pandemic.
The last time Pyongyang invited foreign government delegates for a military parade was in February 2018.
Mr Kim had a "friendly talk" with Mr Shoigu, who handed him an autographed letter from Russian President Vladimir Putin, KCNA said, adding that he had later called North Korea's military "the most powerful" in the world.
The visiting Chinese delegation, led by politburo member Li Hongzhong, also handed a personal letter from Mr Xi to Mr Kim.
Mr Kim reportedly told Mr Li that "the Korean people will never forget the fact that the brave soldiers of the Chinese People's Volunteers shed blood to bring about the war victory".
Beijing had sent troops in the autumn of 1950 to support North Korea in the war against South Korea. The then Soviet Union also supported North Korea in the war.
Since the collapse of the USSR in 1991, Russia has remained a natural ally for North Korea because of their mutual dislike for the US.
Some analysts say the inclusion of Chinese and Russian envoys in this year's Victory Day parade hints at a possible loosening of Covid restrictions.
This comes weeks after images of North Koreans walking around without masks were shown on state media.
The reclusive country had sealed itself off from all trade and diplomatic ties in early 2020, even with Russia and China, its main economic and political partners.
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